Bed RestHead-Down TiltWeightlessness SimulationInfluenza, HumanInfluenza A Virus, H1N1 SubtypeWeightlessness CountermeasuresRestSeverity of Illness IndexCardiovascular DeconditioningHospitalizationDisease OutbreaksSpace FlightInfant, NewbornPandemicsBedsWeightlessnessInfluenza VaccinesIntensive Care UnitsPopulation SurveillanceSeasonsOrthostatic IntoleranceRisk FactorsAntiviral AgentsTime FactorsLower Body Negative PressureAntibodies, ViralProspective StudiesVaccinationUnited StatesPregnancyPrevalenceAnti-Bacterial AgentsRetrospective StudiesBed OccupancyCost of IllnessCritical IllnessMuscular AtrophySupine PositionEarly AmbulationExerciseMuscle, SkeletalPlasma VolumeHypotension, OrthostaticHypovolemiaVascular CapacitanceAmino Acids, EssentialImmobilizationSpinal Puncture