Association of respiratory virus activity and environmental factors with the incidence of invasive pneumococcal disease

Objectives: To correlate the incidence rate of invasive pneumococcal disease (IPD) with fluctuations in respiratory virus activity and environmental factors in Christchurch, New Zealand. Methods. Ecological study comparing incidence rates of IPD with incidence rates of respiratory virus detection, meteorologic and air pollution data during 1995-2006. The relationship between annualized monthly rates of IPD and annualized monthly rates of respiratory virus detection and monthly meteorologic recordings and air pollution data was assessed using Spearman's rank correlation coefficient and negative binomial regression analysis. Results: Incidence rates of IPD were statistically significantly correlated with increasing detection rates of influenza viruses, respiratory syncytial virus (RSV), adenovirus and parainfluenza virus 3. Furthermore, rates of IPD were statistically significantly correlated with decreasing daily temperature, sunshine hours and wind speed, and with increasing air pollution levels and humidity. After regression analysis, the only statistically significant associations in the total population were between influenza virus activity, parainfluenza virus 3 activity and air pollution levels and increased rates of IPD, although RSV activity was associated with increased rates of IPD in children <5 years old. Conclusions: Incidence rates of IPD are associated with the increased activity of some respiratory viruses and with air pollution in Christchurch. (C) 2008 The British Infection Society. Published by Elsevier Ltd. All rights reserved.