The association between climate, geography and respiratory syncitial virus hospitalizations among children in Ontario, Canada: a population-based study

Background: Respiratory syncytial virus (RSV) infection is a major cause of hospitalization in young children in Canada, despite routine immunoprophylaxis in those with medical risk factors. We aimed to determine if cold temperatures are associated with RSV hospitalization. Methods: We conducted a population-based nested case–control study of children in Ontario, Canada, using health administrative data. We compared children hospitalized for RSV between September 1, 2011 and August 31, 2012 to age and sex matched controls. We used multivariable logistic regression to identify associations between minimum daily temperature and RSV hospitalizations with adjustment for sociodemographic and environmental factors. Results: We identified 1670 children with RSV hospitalizations during the study period and 6680 matched controls. Warmer temperatures (OR=0.94, 95%CI: 0.93, 0.95) were associated with lower odds of RSV hospitalization. Southern ecozone (OR=1.6, 95%CI: 1.2, 2.1), increased ozone concentration (OR=1.03, 95%CI: 1.01, 1.06) and living in a lower income neighbourhood (OR=1.3, 95%CI: 1.1, 1.5) significantly increased the odds of RSV hospitalization, as did living in a household with a larger number of siblings in a sub-cohort of children (OR=1.34, 95%CI: 1.26, 1.41). Conclusions: In Ontario, the likelihood of having an RSV hospitalization is associated with colder temperature exposures and socioeconomic factors.