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  <xs:element id="bcrx_ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" abstract="false" name="ExpectedReceivableFromAwardsForResearchAndDevelopmentContracts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
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  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSales" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
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  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInKeyTerritories" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInKeyTerritories" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
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  <xs:element id="bcrx_FutureRoyaltiesPayableMember" abstract="true" name="FutureRoyaltiesPayableMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesUnder15BillionMember" abstract="true" name="AnnualNetSalesUnder15BillionMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_RoyaltyExpenseReversalOfExpense" abstract="false" name="RoyaltyExpenseReversalOfExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_MaturityPeriodOfHighQualityMarketableSecurities" abstract="false" name="MaturityPeriodOfHighQualityMarketableSecurities" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_AnnualNetSalesRangeAxis" abstract="true" name="AnnualNetSalesRangeAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_NumberOfProductsObtainedDoses" abstract="false" name="NumberOfProductsObtainedDoses" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcrx_CommonStockPurchaseAgreementWithRPIMember" abstract="true" name="CommonStockPurchaseAgreementWithRPIMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_BetweenTheSecondAndThirdAnniversariesMember" abstract="true" name="BetweenTheSecondAndThirdAnniversariesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_InterestReserve" abstract="false" name="InterestReserve" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PrivatePlacementOfSeniorSecuredNotes" abstract="false" name="PrivatePlacementOfSeniorSecuredNotes" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPurchasePriceAmount" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPurchasePriceAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeMilestone" abstract="false" name="PotentialMilestonePaymentsReceivableIfRegulatoryApprovalBeforeMilestone" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_AnnualNetSalesUnder350000Member" abstract="true" name="AnnualNetSalesUnder350000Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_PercentageOfSalaryToPurchaseCommonStockMaximum" abstract="false" name="PercentageOfSalaryToPurchaseCommonStockMaximum" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_UABMember" abstract="true" name="UABMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_RenewablePeriodOfAgreement" abstract="false" name="RenewablePeriodOfAgreement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_DescriptionOfCompanyPolicyTextBlock" abstract="false" name="DescriptionOfCompanyPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="bcrx_ProceedsFromAwardsForResearchAndDevelopmentContracts" abstract="false" name="ProceedsFromAwardsForResearchAndDevelopmentContracts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_DebtCovenantTermsAxis" abstract="true" name="DebtCovenantTermsAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_DebtCovenantTermsDomain" abstract="true" name="DebtCovenantTermsDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_ProceedsFromDebtInstrumentCommitmentFee" abstract="false" name="ProceedsFromDebtInstrumentCommitmentFee" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_OperatingLeaseAssets" abstract="true" name="OperatingLeaseAssets" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="bcrx_ContractTerm" abstract="false" name="ContractTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_ASPRBARDAContractMember" abstract="true" name="ASPRBARDAContractMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" abstract="true" name="VestUponSuccessfulCompletionOfSpecificDevelopmentMilestonesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AnnualNetSalesRangeDomain" abstract="true" name="AnnualNetSalesRangeDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_ScheduleOfReceivablesFromCollaborationsTableTextBlock" abstract="false" name="ScheduleOfReceivablesFromCollaborationsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="bcrx_TermCLoanMember" abstract="true" name="TermCLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_InterestExpenseAndRoyaltyFinancingObligationPolicyTextBlock" abstract="false" name="InterestExpenseAndRoyaltyFinancingObligationPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="bcrx_InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" abstract="false" name="InterestExpenseAndDeferredFinancingCostsPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="bcrx_TradeReceivablesTextBlock" abstract="false" name="TradeReceivablesTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="bcrx_AmortizationOfDiscountAndPremiumOnInvestments" abstract="false" name="AmortizationOfDiscountAndPremiumOnInvestments" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_AggregateLeaseExpense" abstract="false" name="AggregateLeaseExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_AnnualNetSalesBetween15And3BillionsMember" abstract="true" name="AnnualNetSalesBetween15And3BillionsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types: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_FutureRoyaltiesPayable" abstract="false" name="FutureRoyaltiesPayable" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_DebtInstrumentCovenantMinimumUnrestrictedCashAndCashEquivalents" abstract="false" name="DebtInstrumentCovenantMinimumUnrestrictedCashAndCashEquivalents" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_RoyaltyMonetizationMember" abstract="true" name="RoyaltyMonetizationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_PriorToTheSecondAnniversaryMember" abstract="true" name="PriorToTheSecondAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_ReceivablesPayablesNetCurrent" abstract="false" name="ReceivablesPayablesNetCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_TransactionCosts" abstract="false" name="TransactionCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_TermBLoanMember" abstract="true" name="TermBLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesMaximumTieredProfitSharePercentageOnPermittedSalesInOtherMarkets" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesMaximumTieredProfitSharePercentageOnPermittedSalesInOtherMarkets" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_InducementPlanMember" abstract="true" name="InducementPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_The2021RPIRoyaltyPurchaseAgreementMember" abstract="true" name="The2021RPIRoyaltyPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_MaximumCustomaryReductionOnRoyaltyRate" abstract="false" name="MaximumCustomaryReductionOnRoyaltyRate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfPurchasePrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployeeAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_PercentageOfCommonStockSharesEnding" abstract="false" name="PercentageOfCommonStockSharesEnding" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_RoyaltyPaymentsReceivableExpirationTermFromFirstCommercial" abstract="false" name="RoyaltyPaymentsReceivableExpirationTermFromFirstCommercial" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="bcrx_AvailableForSaleDebtSecuritiesAccruedInterest" abstract="false" name="AvailableForSaleDebtSecuritiesAccruedInterest" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcrx_RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInOtherMarkets" abstract="false" name="RoyaltyPurchaseAgreementRoyaltiesPercentageOfAnnualNetSalesInOtherMarkets" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcrx_PhaRMANotesMember" abstract="true" name="PhaRMANotesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_AccruedExpensesPolicyTextBlock" abstract="false" name="AccruedExpensesPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="bcrx_MidCapFinancialServicesLLCMember" abstract="true" name="MidCapFinancialServicesLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcrx_StockIssuedDuringPeriodSharesWarrantsExercised" abstract="false" name="StockIssuedDuringPeriodSharesWarrantsExercised" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="bcrx_CollaborativeAgreementContractCovenantMaximumAmountOfFunding" abstract="false" name="CollaborativeAgreementContractCovenantMaximumAmountOfFunding" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
