<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
<!--Generated by ThunderDome XBRL - 06:27PM UTC 2022-02-28--><xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:bcrx="http://www.biocryst.com/20211231" xmlns:country="http://xbrl.sec.gov/country/2021" xmlns:currency="http://xbrl.sec.gov/currency/2021" xmlns:dei="http://xbrl.sec.gov/dei/2021q4" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:exch="http://xbrl.sec.gov/exch/2021" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:naics="http://xbrl.sec.gov/naics/2021" xmlns:sic="http://xbrl.sec.gov/sic/2021" xmlns:srt="http://fasb.org/srt/2021-01-31" xmlns:srt-types="http://fasb.org/srt-types/2021-01-31" xmlns:stpr="http://xbrl.sec.gov/stpr/2021" xmlns:us-gaap="http://fasb.org/us-gaap/2021-01-31" xmlns:us-types="http://fasb.org/us-types/2021-01-31" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.biocryst.com/20211231">
  <xsd:import namespace="http://xbrl.sec.gov/country/2021" schemaLocation="https://xbrl.sec.gov/country/2021/country-2021.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/naics/2021" schemaLocation="https://xbrl.sec.gov/naics/2021/naics-2021.xsd"/>
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xsd:import namespace="http://fasb.org/us-gaap/2021-01-31" schemaLocation="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd"/>
  <xsd:import namespace="http://fasb.org/srt/2021-01-31" schemaLocation="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/dei/2021q4" schemaLocation="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/stpr/2021" schemaLocation="https://xbrl.sec.gov/stpr/2021/stpr-2021.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/sic/2021" schemaLocation="https://xbrl.sec.gov/sic/2021/sic-2021.xsd"/>
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/exch/2021" schemaLocation="https://xbrl.sec.gov/exch/2021/exch-2021.xsd"/>
  <xsd:import namespace="http://fasb.org/us-types/2021-01-31" schemaLocation="https://xbrl.fasb.org/us-gaap/2021/elts/us-types-2021-01-31.xsd"/>
  <xsd:import namespace="http://xbrl.sec.gov/currency/2021" schemaLocation="https://xbrl.sec.gov/currency/2021/currency-2021.xsd"/>
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xsd:import namespace="http://fasb.org/srt-types/2021-01-31" schemaLocation="https://xbrl.fasb.org/srt/2021/elts/srt-types-2021-01-31.xsd"/>
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd"/>
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="bcrx-20211231_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="bcrx-20211231_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="bcrx-20211231_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="bcrx-20211231_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="statement-document-and-entity-information" roleURI="http://www.biocryst.com/20211231/role/statement-document-and-entity-information">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">000 - Document - Document And Entity Information</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-consolidated-balance-sheets-" roleURI="http://www.biocryst.com/20211231/role/statement-consolidated-balance-sheets-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">001 - Statement - Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-consolidated-balance-sheets-parentheticals" roleURI="http://www.biocryst.com/20211231/role/statement-consolidated-balance-sheets-parentheticals">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">002 - Statement - Consolidated Balance Sheets (Parentheticals)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-consolidated-statements-of-comprehensive-loss-" roleURI="http://www.biocryst.com/20211231/role/statement-consolidated-statements-of-comprehensive-loss-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">003 - Statement - Consolidated Statements of Comprehensive Loss</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-consolidated-statements-of-cash-flows" roleURI="http://www.biocryst.com/20211231/role/statement-consolidated-statements-of-cash-flows">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">004 - Statement - Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-consolidated-statements-of-stockholders-equity-deficit-" roleURI="http://www.biocryst.com/20211231/role/statement-consolidated-statements-of-stockholders-equity-deficit-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">005 - Statement - Consolidated Statements of Stockholders' Equity (Deficit)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-consolidated-statements-of-stockholders-equity-deficit-parentheticals" roleURI="http://www.biocryst.com/20211231/role/statement-consolidated-statements-of-stockholders-equity-deficit-parentheticals">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">006 - Statement - Consolidated Statements of Stockholders' Equity (Deficit) (Parentheticals)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-1-significant-accounting-policies-and-concentrations-of-risk" roleURI="http://www.biocryst.com/20211231/role/statement-note-1-significant-accounting-policies-and-concentrations-of-risk">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">007 - Disclosure - Note 1 - Significant Accounting Policies and Concentrations of Risk</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-2-revenue-" roleURI="http://www.biocryst.com/20211231/role/statement-note-2-revenue-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">008 - Disclosure - Note 2 - Revenue</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-3-investments-" roleURI="http://www.biocryst.com/20211231/role/statement-note-3-investments-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">009 - Disclosure - Note 3 - Investments</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-4-trade-receivables-" roleURI="http://www.biocryst.com/20211231/role/statement-note-4-trade-receivables-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">010 - Disclosure - Note 4 - Trade Receivables</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-inventory-" roleURI="http://www.biocryst.com/20211231/role/statement-note-5-inventory-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">011 - Disclosure - Note 5 - Inventory</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-property-and-equipment" roleURI="http://www.biocryst.com/20211231/role/statement-note-6-property-and-equipment">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">012 - Disclosure - Note 6 - Property and Equipment</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-accrued-expenses-" roleURI="http://www.biocryst.com/20211231/role/statement-note-7-accrued-expenses-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">013 - Disclosure - Note 7 - Accrued Expenses</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-8-royalty-monetizations" roleURI="http://www.biocryst.com/20211231/role/statement-note-8-royalty-monetizations">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">014 - Disclosure - Note 8 - Royalty Monetizations</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-debt" roleURI="http://www.biocryst.com/20211231/role/statement-note-9-debt">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">015 - Disclosure - Note 9 - Debt</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-lease-obligations" roleURI="http://www.biocryst.com/20211231/role/statement-note-10-lease-obligations">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">016 - Disclosure - Note 10 - Lease Obligations</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockholders-equity" roleURI="http://www.biocryst.com/20211231/role/statement-note-11-stockholders-equity">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">017 - Disclosure - Note 11 - Stockholders' Equity</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">018 - Disclosure - Note 12 - Stock-based Compensation</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">019 - Disclosure - Note 13 - Income Taxes</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-14-employee-401k-plan-" roleURI="http://www.biocryst.com/20211231/role/statement-note-14-employee-401k-plan-">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">020 - Disclosure - Note 14 - Employee 401(k) Plan</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-15-collaborative-and-other-relationships" roleURI="http://www.biocryst.com/20211231/role/statement-note-15-collaborative-and-other-relationships">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">021 - Disclosure - Note 15- Collaborative and Other Relationships</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-significant-accounting-policies-policies" roleURI="http://www.biocryst.com/20211231/role/statement-significant-accounting-policies-policies">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">022 - Disclosure - Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-2-revenue-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-2-revenue-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">023 - Disclosure - Note 2 - Revenue (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-3-investments-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-3-investments-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">024 - Disclosure - Note 3 - Investments (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-4-trade-receivables-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-4-trade-receivables-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">025 - Disclosure - Note 4 - Trade Receivables (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-inventory-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-5-inventory-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">026 - Disclosure - Note 5 - Inventory (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-property-and-equipment-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-6-property-and-equipment-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">027 - Disclosure - Note 6 - Property and Equipment (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-accrued-expenses-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-7-accrued-expenses-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">028 - Disclosure - Note 7 - Accrued Expenses (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-8-royalty-monetizations-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-8-royalty-monetizations-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">029 - Disclosure - Note 8 - Royalty Monetizations (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-lease-obligations-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-10-lease-obligations-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">030 - Disclosure - Note 10 - Lease Obligations (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">031 - Disclosure - Note 12 - Stock-based Compensation (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-tables" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-tables">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">032 - Disclosure - Note 13 - Income Taxes (Tables)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-1-significant-accounting-policies-and-concentrations-of-risk-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-1-significant-accounting-policies-and-concentrations-of-risk-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">033 - Disclosure - Note 1 - Significant Accounting Policies and Concentrations of Risk (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-2-revenue-summary-of-revenues-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-2-revenue-summary-of-revenues-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">034 - Disclosure - Note 2 - Revenue - Summary of Revenues (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-3-investments-fair-value-of-the-companys-investments-by-type-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-3-investments-fair-value-of-the-companys-investments-by-type-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">035 - Disclosure - Note 3 - Investments- Fair Value of the Company's Investments by Type (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-3-investment-schedule-of-maturity-of-investments-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-3-investment-schedule-of-maturity-of-investments-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">036 - Disclosure - Note 3 - Investment - Schedule of Maturity of Investments (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-4-trade-receivables-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-4-trade-receivables-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">037 - Disclosure - Note 4 - Trade Receivables (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-4-trade-receivables-summary-of-receivables-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-4-trade-receivables-summary-of-receivables-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">038 - Disclosure - Note 4 - Trade Receivables - Summary of Receivables (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-5-inventory-summary-of-inventories-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-5-inventory-summary-of-inventories-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">039 - Disclosure - Note 5 - Inventory - Summary of Inventories (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-property-and-equipment-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-6-property-and-equipment-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">040 - Disclosure - Note 6 - Property and Equipment (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-6-property-and-equipment-property-and-equipment-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-6-property-and-equipment-property-and-equipment-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">041 - Disclosure - Note 6 - Property and Equipment - Property and Equipment (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-7-accrued-expenses-accrued-expenses-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-7-accrued-expenses-accrued-expenses-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">042 - Disclosure - Note 7 - Accrued Expenses - Accrued Expenses (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-8-royalty-monetizations-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-8-royalty-monetizations-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">043 - Disclosure - Note 8 - Royalty Monetizations (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-8-royalty-monetizations-schedule-of-royalty-financing-obligations-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-8-royalty-monetizations-schedule-of-royalty-financing-obligations-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">044 - Disclosure - Note 8 - Royalty Monetizations - Schedule of Royalty Financing Obligations (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-9-debt-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-9-debt-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">045 - Disclosure - Note 9 - Debt (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-lease-obligations-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-10-lease-obligations-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">046 - Disclosure - Note 10 - Lease Obligations (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-lease-obligations-balance-sheets-of-the-companys-operating-leases-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-10-lease-obligations-balance-sheets-of-the-companys-operating-leases-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">047 - Disclosure - Note 10 - Lease Obligations -Balance Sheets of the Company's Operating Leases (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-10-lease-obligations-maturities-of-operating-lease-liabilities-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-10-lease-obligations-maturities-of-operating-lease-liabilities-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">048 - Disclosure - Note 10 - Lease Obligations - Maturities of Operating Lease Liabilities (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-11-stockholders-equity-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-11-stockholders-equity-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">049 - Disclosure - Note 11 - Stockholders' Equity (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">050 - Disclosure - Note 12 - Stock-based Compensation (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-stockbased-compensation-allocation-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-stockbased-compensation-allocation-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">051 - Disclosure - Note 12 - Stock-Based Compensation - Stock-based Compensation Allocation (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-stock-plan-activities-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-stock-plan-activities-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">052 - Disclosure - Note 12 - Stock-based Compensation - Stock Plan Activities (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-plans-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-plans-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">053 - Disclosure - Note 12 - Stock-based Compensation - Weighted Average Assumptions for Stock Option Awards Granted to Employees and Directors Under the Plans (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">054 - Disclosure - Note 12 - Stock-based Compensation - Number of Stock Option Awards Exercisable and their Weighted Average Exercise Price (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-12-stockbased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-12-stockbased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">055 - Disclosure - Note 12 - Stock-based Compensation - Changes in the Number and Weighted-Average Grant-Date Fair Value (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">056 - Disclosure - Note 13 - Income Taxes (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-loss-before-provision-for-income-taxes-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-loss-before-provision-for-income-taxes-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">057 - Disclosure - Note 13 - Income Taxes - Loss Before Provision for Income Taxes (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">058 - Disclosure - Note 13 - Income Taxes - Differences Between the Company's Effective Tax Rate and the Statutory Tax Rate (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">059 - Disclosure - Note 13 - Income Taxes - Differences Between the Company's Effective Tax Rate and the Statutory Tax Rate (Details) (Parentheticals)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">060 - Disclosure - Note 13 - Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-13-income-taxes-components-of-deferred-tax-assets-and-liabilities-details" roleURI="http://www.biocryst.com/20211231/role/statement-note-13-income-taxes-components-of-deferred-tax-assets-and-liabilities-details">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">061 - Disclosure - Note 13 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-14-employee-401k-plan-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-14-employee-401k-plan-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">062 - Disclosure - Note 14 - Employee 401(k) Plan (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
      <link:roleType id="statement-note-15-collaborative-and-other-relationships-details-textual" roleURI="http://www.biocryst.com/20211231/role/statement-note-15-collaborative-and-other-relationships-details-textual">
        <link:definition xmlns="http://www.xbrl.org/2003/linkbase">063 - Disclosure - Note 15- Collaborative and Other Relationships (Details Textual)</link:definition>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
        <link:usedOn>link:presentationLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element abstract="true" id="bcrx_AECOMAndIRLMember" name="AECOMAndIRLMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ASPRBARDAContractMember" name="ASPRBARDAContractMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_AccruedDevelopmentCosts" name="AccruedDevelopmentCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_AccruedExpensesPolicyTextBlock" name="AccruedExpensesPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_AccruedInventoryExpense" name="AccruedInventoryExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_AccruedLiabilitiesCurrentAndOtherNoncurrentLiabilitiesMember" name="AccruedLiabilitiesCurrentAndOtherNoncurrentLiabilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AdditionalDevelopmentOptionsMember" name="AdditionalDevelopmentOptionsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AfterFourthAnniversaryMember" name="AfterFourthAnniversaryMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_AmortizationOfDebtFinancingCostsAndOriginalIssueDiscounts" name="AmortizationOfDebtFinancingCostsAndOriginalIssueDiscounts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_AmortizationOfDiscountAndPremiumOnInvestments" name="AmortizationOfDiscountAndPremiumOnInvestments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_AnnualLicenseFeeMaximum" name="AnnualLicenseFeeMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_AnnualLicenseFeeMinimum" name="AnnualLicenseFeeMinimum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesBetween150000And230000Member" name="AnnualNetSalesBetween150000And230000Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesBetween15And3BillionsMember" name="AnnualNetSalesBetween15And3BillionsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesBetween350000And550000Member" name="AnnualNetSalesBetween350000And550000Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesOver230000Member" name="AnnualNetSalesOver230000Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesOver3BillionsMember" name="AnnualNetSalesOver3BillionsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesOver550000Member" name="AnnualNetSalesOver550000Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesUnder150000Member" name="AnnualNetSalesUnder150000Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesUnder15BillionMember" name="AnnualNetSalesUnder15BillionMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AnnualNetSalesUnder350000Member" name="AnnualNetSalesUnder350000Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ArbitrationProceedingsOfSulAgreementMember" name="ArbitrationProceedingsOfSulAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_AthyriumMember" name="AthyriumMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_August2013Member" name="August2013Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest" name="AvailableForSaleDebtSecuritiesAccruedInterest" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities" name="AverageMaturityPeriodOfHighQualityMarketableSecurities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_BCX9930Member" name="BCX9930Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_BaseContractMember" name="BaseContractMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_BetweenTheSecondAndThirdAnniversariesMember" name="BetweenTheSecondAndThirdAnniversariesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_BetweenTheThirdAndFourthAnniversariesMember" name="BetweenTheThirdAndFourthAnniversariesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_CSLLimitedMember" name="CSLLimitedMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ClassOfWarrantOrRightIssuedDuringPeriod" name="ClassOfWarrantOrRightIssuedDuringPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ClassOfWarrantOrRightWarrantsIssuedPricePerWarrant" name="ClassOfWarrantOrRightWarrantsIssuedPricePerWarrant" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_CollaborativeAgreementContractCovenantMaximumAmountOfFunding" name="CollaborativeAgreementContractCovenantMaximumAmountOfFunding" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_CollaborativeAgreementContractValue" name="CollaborativeAgreementContractValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember" name="CollaborativeAndOtherResearchAndDevelopmentMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_CollateralForCreditMember" name="CollateralForCreditMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_CommonStockPurchaseAgreementWithRPIMember" name="CommonStockPurchaseAgreementWithRPIMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ConcentrationOfMarketRiskPolicyTextBlock" name="ConcentrationOfMarketRiskPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ContractTerm" name="ContractTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_CreditAgreementMember" name="CreditAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_CurrencyHedgeAgreementPolicyTextBlock" name="CurrencyHedgeAgreementPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_DebtInstrumentCommitmentFeePercentage" name="DebtInstrumentCommitmentFeePercentage" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DebtInstrumentCovenantMinimumUnrestrictedCashAndCashEquivalents" name="DebtInstrumentCovenantMinimumUnrestrictedCashAndCashEquivalents" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DebtInstrumentExitFeePercentageOfPrincipal" name="DebtInstrumentExitFeePercentageOfPrincipal" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DebtInstrumentLiborCap" name="DebtInstrumentLiborCap" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DebtInstrumentLiborFloor" name="DebtInstrumentLiborFloor" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DebtInstrumentMinimumLibor" name="DebtInstrumentMinimumLibor" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_DebtInstrumentPrepaymentFeePercentageOfAccruedInterest" name="DebtInstrumentPrepaymentFeePercentageOfAccruedInterest" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_DebtInstrumentPrepaymentFeePercentageOfPrincipalVoluntaryPayments" name="DebtInstrumentPrepaymentFeePercentageOfPrincipalVoluntaryPayments" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_DebtSecuritiesAvailableforsaleFairValueMaturityAllocatedAndSingleMaturityDateAfterYearOneThroughTwo" name="DebtSecuritiesAvailableforsaleFairValueMaturityAllocatedAndSingleMaturityDateAfterYearOneThroughTwo" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_December2019Member" name="December2019Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_DeferredTaxAssetsLeasingObligations" name="DeferredTaxAssetsLeasingObligations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DeferredTaxAssetsRoyaltyIncome" name="DeferredTaxAssetsRoyaltyIncome" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DeferredTaxLiabilitiesRightOfUseAssets" name="DeferredTaxLiabilitiesRightOfUseAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_DescriptionOfCompanyPolicyTextBlock" name="DescriptionOfCompanyPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_DocumentAndEntityInformation" name="DocumentAndEntityInformation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour" name="EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearFour" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree" name="EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearThree" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo" name="EmployeeServiceShareBasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedYearTwo" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear" name="EmployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostExpectedToBeRecognizedNextYear" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ExercisePriceRange01Member" name="ExercisePriceRange01Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ExercisePriceRange02Member" name="ExercisePriceRange02Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ExercisePriceRange03Member" name="ExercisePriceRange03Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ExercisePriceRange04Member" name="ExercisePriceRange04Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ExercisePriceRange05Member" name="ExercisePriceRange05Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ExercisePriceRange06Member" name="ExercisePriceRange06Member" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" name="ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_FutureRoyaltiesPayable" name="FutureRoyaltiesPayable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_FutureRoyaltiesPayableMember" name="FutureRoyaltiesPayableMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_GreenCrossCorporationMember" name="GreenCrossCorporationMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_IncentivePlanAndInducementPlanMember" name="IncentivePlanAndInducementPlanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_IncentivePlanMember" name="IncentivePlanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards" name="IncomeTaxReconciliationIncomeTaxExpenseBenefitExpirationOfCarryForwards" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_IncreaseDecreaseInExtinguishmentOfDebt" name="IncreaseDecreaseInExtinguishmentOfDebt" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_InducementPlanMember" name="InducementPlanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_InterestAndOtherIncomeLoss" name="InterestAndOtherIncomeLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" name="InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_InterestExpenseAndRoyaltyFinancingObligationPolicyTextBlock" name="InterestExpenseAndRoyaltyFinancingObligationPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_InterestReserve" name="InterestReserve" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_JPRRoyaltySubLLCMember" name="JPRRoyaltySubLLCMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_LaboratoryEquipmentMember" name="LaboratoryEquipmentMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_LaboratoryEquipmentOfficeEquipmentAndSoftwareMember" name="LaboratoryEquipmentOfficeEquipmentAndSoftwareMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_LesseeOperatingLeaseAssetsAndLiabilitiesTableTextBlock" name="LesseeOperatingLeaseAssetsAndLiabilitiesTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_LongtermInvestmentMaturityMinimum" name="LongtermInvestmentMaturityMinimum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_MaturityPeriodOfHighQualityMarketablesecurities" name="MaturityPeriodOfHighQualityMarketablesecurities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_MaturityperiodOfShortTermInvestment" name="MaturityperiodOfShortTermInvestment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_MaximumAggregateOfferingPrice" name="MaximumAggregateOfferingPrice" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_MaximumCustomaryReductionOnRoyaltyRate" name="MaximumCustomaryReductionOnRoyaltyRate" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_MaximumNumberOfProductsPermittedToBeObtainedDoses" name="MaximumNumberOfProductsPermittedToBeObtainedDoses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_MidCapFinancialServicesLLCMember" name="MidCapFinancialServicesLLCMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_MilestoneMember" name="MilestoneMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_MilestonePaymentMaximum" name="MilestonePaymentMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_MilestonePaymentMinimum" name="MilestonePaymentMinimum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_MilestonePaymentReceived" name="MilestonePaymentReceived" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_NationalInstituteOfAllergyAndInfectiousDiseasesMember" name="NationalInstituteOfAllergyAndInfectiousDiseasesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_NonCashInterestExpenseOnRoyaltyFinancingObligation" name="NonCashInterestExpenseOnRoyaltyFinancingObligation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_NonEmployeeDirectorsMember" name="NonEmployeeDirectorsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_NoncashInterestExpenseAndAmortizationOfDebtIssuanceCosts" name="NoncashInterestExpenseAndAmortizationOfDebtIssuanceCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_NoteToFinancialStatementDetailsTextual" name="NoteToFinancialStatementDetailsTextual" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_NotesToFinancialStatements" name="NotesToFinancialStatements" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_NotesToFinancialStatementsAbstract" name="NotesToFinancialStatementsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_NumberOfAdditionalProductsDoses" name="NumberOfAdditionalProductsDoses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_NumberOfProductDeliveredDoses" name="NumberOfProductDeliveredDoses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_OMERSCapitalMarketsMember" name="OMERSCapitalMarketsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_OMERSRoyaltyAgreementMember" name="OMERSRoyaltyAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ORLADEYOMember" name="ORLADEYOMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_OperatingLeaseAssets" name="OperatingLeaseAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_OperatingLeaseRightofuseAssetAccumulatedAmortization" name="OperatingLeaseRightofuseAssetAccumulatedAmortization" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_PERAMIVIRMember" name="PERAMIVIRMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_PercentageOfCommonStockSharesBeginning" name="PercentageOfCommonStockSharesBeginning" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_PercentageOfCommonStockSharesEnding" name="PercentageOfCommonStockSharesEnding" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum" name="PercentageOfSalaryToPurchaseCommonStockMaximum" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_PeriodOfAgreement" name="PeriodOfAgreement" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_PhaRMANotesMember" name="PhaRMANotesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_PikInterestPaymentIsMadeMember" name="PikInterestPaymentIsMadeMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeDecember312021" name="PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeDecember312021" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_PriorToTheSecondAnniversaryMember" name="PriorToTheSecondAnniversaryMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_PrivatePlacementOfSeniorSecuredNotes" name="PrivatePlacementOfSeniorSecuredNotes" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts" name="ProceedsFromAwardsForResearchAndDevelopmentContracts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ProceedsFromRoyaltyFinancingObligation" name="ProceedsFromRoyaltyFinancingObligation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_RAPIVABMember" name="RAPIVABMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_RPI2019IntermediateFinanceTrustMember" name="RPI2019IntermediateFinanceTrustMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_RPI2021And2020IntermediateFinanceTrustMember" name="RPI2021And2020IntermediateFinanceTrustMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ReceivablesPayablesNetCurrent" name="ReceivablesPayablesNetCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_ReclassificationsPolicyTextBlock" name="ReclassificationsPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RenewablePeriodOfAgreement" name="RenewablePeriodOfAgreement" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltiesPayable" name="RoyaltiesPayable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_RoyaltiesRevenuesPaidAndPayable" name="RoyaltiesRevenuesPaidAndPayable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyExpenseReversalOfExpense" name="RoyaltyExpenseReversalOfExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyFinancingObligationsTableTextBlock" name="RoyaltyFinancingObligationsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_RoyaltyMonetizationMember" name="RoyaltyMonetizationMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyMonetizationTextBlock" name="RoyaltyMonetizationTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPaymentsReceivableExpirationTermFromFirstCommercial" name="RoyaltyPaymentsReceivableExpirationTermFromFirstCommercial" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesAnnualNetSalesPaymentThreshold" name="RoyaltyPurchaseAgreementRoyaltiesAnnualNetSalesPaymentThreshold" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesMaximumTieredProfitSharePercentageOnPermittedSalesInOtherMarkets" name="RoyaltyPurchaseAgreementRoyaltiesMaximumTieredProfitSharePercentageOnPermittedSalesInOtherMarkets" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInKeyTerritories" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInKeyTerritories" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInOtherMarkets" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInOtherMarkets" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfGlobalAnnualNetSales" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfGlobalAnnualNetSales" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfSublicenseRevenueInOtherMarkets" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfSublicenseRevenueInOtherMarkets" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPurchasePriceAmount" name="RoyaltyPurchaseAgreementRoyaltiesPurchasePriceAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_RoyaltyRateIfMaintainsSakigakeDesignation" name="RoyaltyRateIfMaintainsSakigakeDesignation" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_RoyaltyReceivableMember" name="RoyaltyReceivableMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_RoyaltyReceivablesFromPartnersMember" name="RoyaltyReceivablesFromPartnersMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock" name="ScheduleOfReceivablesFromCollaborationsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_SecuredCreditFacilityFirstTrancheMember" name="SecuredCreditFacilityFirstTrancheMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_SecuredCreditFacilitySecondTrancheMember" name="SecuredCreditFacilitySecondTrancheMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_SecuredCreditFacilityThirdTrancheMember" name="SecuredCreditFacilityThirdTrancheMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_SeniorCreditFacilityMember" name="SeniorCreditFacilityMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodAwardsAvailable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_ShareBasedCompensationArrangementBySharebasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" name="ShareBasedCompensationArrangementBySharebasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable" name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsForfeituresInPeriodAwardsAvailable" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_SharesIssuedCommonStockPremium" name="SharesIssuedCommonStockPremium" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_SharesIssuedPricePerShareClosingPrice" name="SharesIssuedPricePerShareClosingPrice" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType" xbrli:periodType="instant"/>
  <xsd:element id="bcrx_SharesIssuedPricePerSharePremium" name="SharesIssuedPricePerSharePremium" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType" xbrli:periodType="instant"/>
  <xsd:element abstract="true" id="bcrx_TermALoanMember" name="TermALoanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TermBLoanMember" name="TermBLoanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TermCLoanMember" name="TermCLoanMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TermLoanAAndBDrawnMember" name="TermLoanAAndBDrawnMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TermLoanADrawnMember" name="TermLoanADrawnMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TermLoansABAndCDrawnAndCureRightExercisedMember" name="TermLoansABAndCDrawnAndCureRightExercisedMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TermLoansABAndCDrawnMember" name="TermLoansABAndCDrawnMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_The2021RPIRoyaltyPurchaseAgreementMember" name="The2021RPIRoyaltyPurchaseAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ThirtysixEqualMonthlyInstallmentsMember" name="ThirtysixEqualMonthlyInstallmentsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_ToriiPharmaceuticalCoMember" name="ToriiPharmaceuticalCoMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_TradeReceivablesTextBlock" name="TradeReceivablesTextBlock" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType" xbrli:periodType="duration"/>
  <xsd:element id="bcrx_TransactionCosts" name="TransactionCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TwentyTwentyOneRPIRoyaltyAgreementMember" name="TwentyTwentyOneRPIRoyaltyAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_TwentyTwentyRPIRoyaltyAgreementMember" name="TwentyTwentyRPIRoyaltyAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_UABMember" name="UABMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_USDepartmentOfHealthAndHumanServicesMember" name="USDepartmentOfHealthAndHumanServicesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_Vest25PercentEachYearUntilFullyVestedMember" name="Vest25PercentEachYearUntilFullyVestedMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" name="VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_WarrantsIssuedInPublicOfferingMember" name="WarrantsIssuedInPublicOfferingMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-10-lease-obligations-balance-sheets-of-the-companys-operating-leases-details" name="statement-statement-note-10-lease-obligations-balance-sheets-of-the-companys-operating-leases-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-10-lease-obligations-maturities-of-operating-lease-liabilities-details" name="statement-statement-note-10-lease-obligations-maturities-of-operating-lease-liabilities-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-10-lease-obligations-tables" name="statement-statement-note-10-lease-obligations-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-12-stockbased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details" name="statement-statement-note-12-stockbased-compensation-changes-in-the-number-and-weightedaverage-grantdate-fair-value-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-12-stockbased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details" name="statement-statement-note-12-stockbased-compensation-number-of-stock-option-awards-exercisable-and-their-weighted-average-exercise-price-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-12-stockbased-compensation-stock-plan-activities-details" name="statement-statement-note-12-stockbased-compensation-stock-plan-activities-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-12-stockbased-compensation-stockbased-compensation-allocation-details" name="statement-statement-note-12-stockbased-compensation-stockbased-compensation-allocation-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-12-stockbased-compensation-tables" name="statement-statement-note-12-stockbased-compensation-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-12-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-plans-details" name="statement-statement-note-12-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-plans-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-13-income-taxes-components-of-deferred-tax-assets-and-liabilities-details" name="statement-statement-note-13-income-taxes-components-of-deferred-tax-assets-and-liabilities-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details" name="statement-statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals" name="statement-statement-note-13-income-taxes-differences-between-the-companys-effective-tax-rate-and-the-statutory-tax-rate-details-parentheticals" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-13-income-taxes-loss-before-provision-for-income-taxes-details" name="statement-statement-note-13-income-taxes-loss-before-provision-for-income-taxes-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-13-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details" name="statement-statement-note-13-income-taxes-reconciliation-of-beginning-and-ending-amount-of-unrecognized-tax-benefits-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-13-income-taxes-tables" name="statement-statement-note-13-income-taxes-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-2-revenue-summary-of-revenues-details" name="statement-statement-note-2-revenue-summary-of-revenues-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-2-revenue-tables" name="statement-statement-note-2-revenue-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-3-investment-schedule-of-maturity-of-investments-details" name="statement-statement-note-3-investment-schedule-of-maturity-of-investments-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-3-investments-fair-value-of-the-companys-investments-by-type-details" name="statement-statement-note-3-investments-fair-value-of-the-companys-investments-by-type-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-3-investments-tables" name="statement-statement-note-3-investments-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-4-trade-receivables-summary-of-receivables-details" name="statement-statement-note-4-trade-receivables-summary-of-receivables-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-4-trade-receivables-tables" name="statement-statement-note-4-trade-receivables-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-5-inventory-summary-of-inventories-details" name="statement-statement-note-5-inventory-summary-of-inventories-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-5-inventory-tables" name="statement-statement-note-5-inventory-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-6-property-and-equipment-property-and-equipment-details" name="statement-statement-note-6-property-and-equipment-property-and-equipment-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-6-property-and-equipment-tables" name="statement-statement-note-6-property-and-equipment-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-7-accrued-expenses-accrued-expenses-details" name="statement-statement-note-7-accrued-expenses-accrued-expenses-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-7-accrued-expenses-tables" name="statement-statement-note-7-accrued-expenses-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-8-royalty-monetizations-schedule-of-royalty-financing-obligations-details" name="statement-statement-note-8-royalty-monetizations-schedule-of-royalty-financing-obligations-details" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-8-royalty-monetizations-tables" name="statement-statement-note-8-royalty-monetizations-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-significant-accounting-policies-policies" name="statement-statement-significant-accounting-policies-policies" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
</xsd:schema>
