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  <xs:element id="bcrx_AverageMaturityPeriodOfHighQualityMarketableSecurities" abstract="false" name="AverageMaturityPeriodOfHighQualityMarketableSecurities" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_StockIssuedDuringPeriodSharesWarrantsExercised" abstract="false" name="StockIssuedDuringPeriodSharesWarrantsExercised" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="bcrx_AuditInformationAbstract" abstract="true" name="AuditInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_RoyaltyReceivableMember" abstract="true" name="RoyaltyReceivableMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_MaturityPeriodOfShortTermInvestment" abstract="false" name="MaturityPeriodOfShortTermInvestment" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_MidCapFinancialServicesLLCMember" abstract="true" name="MidCapFinancialServicesLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_DebtInstrumentExitFeePercentageOfPrincipal" abstract="false" name="DebtInstrumentExitFeePercentageOfPrincipal" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_RPI2021And2020IntermediateFinanceTrustMember" abstract="true" name="RPI2021And2020IntermediateFinanceTrustMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesBasedOnReductionInSales" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_AfterFourthAnniversaryMember" abstract="true" name="AfterFourthAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_TermLoanTrancheDMember" abstract="true" name="TermLoanTrancheDMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_CollaborativeAndOtherResearchAndDevelopmentMember" abstract="true" name="CollaborativeAndOtherResearchAndDevelopmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_ProceedsFromRoyaltyFinancingObligation" abstract="false" name="ProceedsFromRoyaltyFinancingObligation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_CommonStockPurchaseAgreementWithRPIMember" abstract="true" name="CommonStockPurchaseAgreementWithRPIMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_NonEmployeeDirectorsMember" abstract="true" name="NonEmployeeDirectorsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_StockIssuedDuringPeriodValueWarrantsExercised" abstract="false" name="StockIssuedDuringPeriodValueWarrantsExercised" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_OMERSRoyaltyAgreementMember" abstract="true" name="OMERSRoyaltyAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeDecember312021" abstract="false" name="PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeDecember312021" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PotentialMilestonePaymentsPayableIfRegulatoryApprovalBeforeMilestone" abstract="false" name="PotentialMilestonePaymentsPayableIfRegulatoryApprovalBeforeMilestone" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PerformancebasedRestrictedStockUnitsMember" abstract="true" name="PerformancebasedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_Vest25PercentEachYearUntilFullyVestedMember" abstract="true" name="Vest25PercentEachYearUntilFullyVestedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_InterestAndOtherIncomeLoss" abstract="false" name="InterestAndOtherIncomeLoss" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_LesseeOperatingLeaseAssetsAndLiabilitiesTableTextBlock" abstract="false" name="LesseeOperatingLeaseAssetsAndLiabilitiesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="bcrx_OtherIncomeFromContractWithCustomerMember" abstract="true" name="OtherIncomeFromContractWithCustomerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesBetween350000And550000Member" abstract="true" name="AnnualNetSalesBetween350000And550000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_NonCashInterestExpenseOnRoyaltyFinancingObligation" abstract="false" name="NonCashInterestExpenseOnRoyaltyFinancingObligation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_DebtInstrumentCommitmentFeePercentage" abstract="false" name="DebtInstrumentCommitmentFeePercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="bcrx_TermLoansMember" abstract="true" name="TermLoansMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_ThirtySixEqualMonthlyInstallmentsMember" abstract="true" name="ThirtySixEqualMonthlyInstallmentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="bcrx_JonP.StonehouseMember" abstract="true" name="JonP.StonehouseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
