Particulate matter strongly associated with human Q fever in The Netherlands: an ecological study

There are still questions about the importance of different animal reservoirs and environmental factors that played a role in the large Q fever epidemic in The Netherlands. We therefore investigated the spatial association between reported Q fever cases and different livestock and environmental factors at the national level. A spatial regression analysis was performed, with four-digit postal code areas as the unit of analysis. High level of particulate matter (>= 24.5 mu g/m(3)) with an aerodynamic diameter <10 mu m (PM10) was by far the strongest risk factor for human Q fever with an odds ratio of 10.4 (95% confidence interval 7.0-15.6) using PM10 <24.5 mu g/m(3) as reference, in logistic regression analysis, controlling for differences in animal densities, vegetation and other risk factors. Particulate matter seems to play an important role in the transmission of Q fever from infected animals to humans and should be a focus for further studies on zoonotic infectious diseases and decision-making.