Environmental Exposures and Invasive Meningococcal Disease: An Evaluation of Effects on Varying Time Scales

摘要

Invasive meningococcal disease (IMD) is an important cause of meningitis and bacteremia worldwide. Seasonalnvariation in IMD incidence has long been recognized, but mechanisms responsible for this phenomenon remainnpoorly understood. The authors sought to evaluate the effect of environmental factors on IMD risk in Philadelphia,nPennsylvania, a major urban center. Associations between monthly weather patterns and IMD incidence werenevaluated using multivariable Poisson regression models controlling for seasonal oscillation. Short-term weatherneffects were identified using a case-crossover approach. Both study designs control for seasonal factors that mightnotherwise confound the relation between environment and IMD. Incidence displayed significant wintertime season-nality (for oscillation, P < 0.001), and Poisson regression identified elevated monthly risk with increasing relativenhumidity (per 1% increase, incidence rate ratio ¼ 1.04, 95% confidence interval: 1.004, 1.08). Case-crossovernmethods identified an inverse relation between ultraviolet B radiation index 1–4 days prior to onset and disease riskn(odds ratio ¼ 0.54, 95% confidence interval: 0.34, 0.85). Extended periods of high humidity and acute changes innambient ultraviolet B radiation predict IMD occurrence in Philadelphia. The latter effect may be due to decreasednpathogen survival or virulence and may explain the wintertime seasonality of IMD in temperate regions of NorthnAmerica.