Meteorologic Conditions and Respiratory Syncytial Virus Activity

BACKGROUND:The factors that determine the initiation and persistence of yearly epidemics of respiratory syncytial virus (RSV) bronchiolitis are not well known. A limited number of studies have found that meteorologic conditions could be associated with RSV activity. OBJECTIVES:We analyzed the association of certain atmospheric conditions with RSV activity, as determined by the number of hospitalizations of infants with bronchiolitis in Mallorca (Spain). METHODS:We conducted a retrospective review of the medical records of children ≤ 2 years of age with acute bronchiolitis between January 1995 and December 2006. Climatic data were obtained from a weather station located 15 km from the hospital. The number of RSV hospitalizations were correlated to temperature, barometric pressure, relative humidity and water vapor pressure using different time models and regression analyses. RESULTS:A total of 1495 infants with RSV bronchiolitis were hospitalized during the study period, with a seasonal pattern from November to March. Weekly RSV activity could be predicted (R= 0.88; P < 0.001) by mean temperature and atmospheric pressure. Monthly RSV activity was significantly associated (R= 0.95; P < 0.001) with mean and minimum temperature, water vapor pressure, relative humidity and barometric pressure. The peak of RSV activity was observed within 9°C mean temperature, 5°C minimum temperature, 16°C maximum temperature, 1032 hPa atmospheric pressure, 83% relative humidity and 910 hPa water vapor pressure. CONCLUSIONS:The annual patterns of RSV hospitalizations were strongly associated with the meteorologic conditions. The mean temperature and atmospheric pressure were the main factors that correlated with increases and declines in RSV activity.