Onset timing of influenza epidemics are not well defined and not predictable. To better define and predict the onset time of influenza epidemics, a weighted standard distance was calculated using surveillance data from 11.1 million national influenza-like illnesses generated from the 1999/2000 through 2008/2009 influenza seasons within Japan. In the current study, we demonstrated that the weekly weighted standard distance values, or the measure of spatial compactness of the distribution of reported influenza-like illnesses over a one-week time period, decreased to a minimal value before each seasonal epidemic peak.

Therefore, the lowest weighted standard distance value is a possible indicator for the onset of a nationwide influenza outbreak throughout Japan. This demonstration and definition are important for the analysis of influenza epidemics as well as the planning of preventive measures.

 

Air pollution epidemiology studies usually rely on ambient monitoring networks for exposure assessment. The purpose of this study was to characterize the spatial configuration of the ambient PM10 and PM2.5 monitoring networks in California, and assess their alignment with respect to the AHSMOG cohort.