Health Care CostsCost of IllnessUnited StatesCost-Benefit AnalysisPrevalenceCosts and Cost AnalysisDrug CostsCost ControlDirect Service CostsCost SharingCritical IllnessCost AllocationSeverity of Illness IndexModels, EconomicMental DisordersTime FactorsRisk FactorsQuality-Adjusted Life YearsModels, StatisticalHospitalizationInfant, NewbornIllness BehaviorQuestionnairesReproducibility of ResultsChronic DiseaseRetrospective StudiesCohort StudiesEmployer Health CostsIncidenceProspective StudiesAlgorithmsPopulation SurveillanceAge FactorsTreatment OutcomeModels, TheoreticalRegression AnalysisComputer SimulationSensitivity and SpecificityInfluenza, HumanCross-Sectional StudiesGreat BritainModels, BiologicalRisk AssessmentData CollectionModels, GeneticHealth ResourcesLength of StayLikelihood FunctionsSeasonsMarkov ChainsFeverEngland