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  <xsd:element id="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum" name="PercentageOfSalaryToPurchaseCommonStockMaximum" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:percentItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_PerformancebasedRestrictedStockUnitsMember" name="PerformancebasedRestrictedStockUnitsMember" nillable="true" substitutionGroup="xbrli:item" type="dtr-types:domainItemType" 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 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_RealizedGainLossOnSaleOfInvestmentsInvestingActivities" name="RealizedGainLossOnSaleOfInvestmentsInvestingActivities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" 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_RenewablePeriodOfAgreement" name="RenewablePeriodOfAgreement" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration"/>
  <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_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_statement-statement-note-10-stockbased-compensation-stock-plan-activities-details" name="statement-statement-note-10-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-10-stockbased-compensation-tables" name="statement-statement-note-10-stockbased-compensation-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-10-stockbased-compensation-weighted-average-assumptions-for-stock-option-awards-granted-to-employees-and-directors-under-the-plans-details" name="statement-statement-note-10-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-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-royalty-monetizations-schedule-of-royalty-financing-obligations-details" name="statement-statement-note-6-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-6-royalty-monetizations-tables" name="statement-statement-note-6-royalty-monetizations-tables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration"/>
  <xsd:element abstract="true" id="bcrx_statement-statement-note-8-lease-obligations-balance-sheets-of-the-companys-operating-leases-details" name="statement-statement-note-8-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-8-lease-obligations-maturities-of-operating-lease-liabilities-details" name="statement-statement-note-8-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-8-lease-obligations-tables" name="statement-statement-note-8-lease-obligations-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>
