title: Environmental drivers of the spatiotemporal dynamics of respiratory syncytial virus in the United States.
abstract: Epidemics of respiratory syncytial virus (RSV) are known to occur in wintertime in temperate countries including the United States, but there is a limited understanding of the importance of climatic drivers in determining the seasonality of RSV. In the United States, RSV activity is highly spatially structured, with seasonal peaks beginning in Florida in November through December and ending in the upper Midwest in February-March, and prolonged disease activity in the southeastern US. Using data on both age-specific hospitalizations and laboratory reports of RSV in the US, and employing a combination of statistical and mechanistic epidemic modeling, we examined the association between environmental variables and state-specific measures of RSV seasonality. Temperature, vapor pressure, precipitation, and potential evapotranspiration (PET) were significantly associated with the timing of RSV activity across states in univariate exploratory analyses. The amplitude and timing of seasonality in the transmission rate was significantly correlated with seasonal fluctuations in PET, and negatively correlated with mean vapor pressure, minimum temperature, and precipitation. States with low mean vapor pressure and the largest seasonal variation in PET tended to experience biennial patterns of RSV activity, with alternating years of "early-big" and "late-small" epidemics. Our model for the transmission dynamics of RSV was able to replicate these biennial transitions at higher amplitudes of seasonality in the transmission rate. This successfully connects environmental drivers to the epidemic dynamics of RSV; however, it does not fully explain why RSV activity begins in Florida, one of the warmest states, when RSV is a winter-seasonal pathogen. Understanding and predicting the seasonality of RSV is essential in determining the optimal timing of immunoprophylaxis.
authors.affiliation: Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, Connecticut, United States of America; Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Virginia E
authors.initials: VE
authors.lastname: Pitzer
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Cécile
authors.initials: C
authors.lastname: Viboud
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Wladimir J
authors.initials: WJ
authors.lastname: Alonso
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Tanya
authors.initials: T
authors.lastname: Wilcox
authors.affiliation: Department of Zoology, University of Oxford, Oxford, United Kingdom; Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America.
authors.forename: C Jessica
authors.initials: CJ
authors.lastname: Metcalf
authors.affiliation: Healthcare Cost and Utilization Project, Center for Delivery, Organization and Markets, Agency for Healthcare Research and Quality, US Department of Health and Human Services, Rockville, Maryland, United States of America.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Steiner
authors.affiliation: Epidemiology Branch, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Amber K
authors.initials: AK
authors.lastname: Haynes
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America; Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America.
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Grenfell
mesh_terms: D002675:Child, Preschool; D002980:Climate; D004198:Disease Susceptibility / Q000453:epidemiology; D004777:Environment; D058872:Epidemics; D006801:Humans; D006813:Humidity; D007223:Infant; D008962:Models, Theoretical; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology*; D018113:Respiratory Syncytial Virus, Human / Q000472:pathogenicity; D012621:Seasons; D062211:Spatio-Temporal Analysis; D013696:Temperature; D013997:Time Factors; D014481:United States / Q000453:epidemiology