The association of respiratory viruses, temperature, and other climatic parameters with the incidence of invasive pneumococcal disease in Sydney, Australia

Background. Increases in incidence of invasive pneumococcal disease (IPD) during the colder months of the year in temperate regions are well recognized, but few detailed studies of possible interactions are available. We examined the relationship between virus activity, climatic parameters, and IPD during a winter in which there were separate peak incidences of influenza and respiratory syncytial virus (RSV) infection. Methods. We performed an ecological study that correlated population-based data on IPD and respiratory virus activity in the year 2000 in metropolitan New South Wales, Australia, with climatic parameters, including weekly mean maximum and minimum temperature, relative humidity, rainfall, and wind speed. Results. In children, RSV activity was significantly positively correlated with IPD activity (r = 0.578; P = .002) but not with influenza virus activity. There was a weak inverse relationship between parainfluenza virus activity and IPD activity (r = -0.401; P = .043) and a stronger inverse relationship between weekly mean maximum temperature (r = -0.458; P = .001), weekly mean minimum temperature (r = -0.437; P = .001), and IPD activity. In adults, there was no significant correlation between RSV or influenza virus activity alone and IPD, but the combination of RSV and influenza was significantly correlated with IPD (r = 0.481; P = .013). Conclusions. This study suggests that RSV infection and influenza contribute to IPD incidence peaks differently for children than for adults. Data from other geographic areas and more rigorous study designs are required to confirm these findings.