Does ambient temperature affect foodborne disease?

Background: Foodborne illness is a significant public health issue in most countries, including Australia. We examined the association between temperature and salmonellosis notifications, and compared these associations for 5 Australian cities. Methods: Log-linear models describing monthly salmonellosis notifications in terms of calendar time and monthly average temperatures were fitted over the period 1991 to 2001 for each city. We used a negative binomial chance model to accommodate overdispersion in the counts. Results: The long-term trend showed an increase in salmonellosis notifications in each of the 5 cities. There was a positive association between monthly salmonellosis notifications and mean monthly temperature of the previous month in every city. Seasonal patterns in salmonellosis notifications were fully explained by changes in temperature. Discussion: The strength of the association, the consistency across 5 cities, and a plausible biologic pathway suggest that higher ambient temperatures are a cause of higher salmonellosis notifications. The lag of 1 month suggests that temperature might be more influential earlier in the production process rather than at the food preparation stage. This knowledge can help to guide policy on food preparation and distribution. It also suggests a basis for an early warning system for increased risk from salmonellosis, and raises yet another possible health problem with global warming.