Effects of Temperature on Outbreaks of Salmonella Food Poisoning by Causative Food.

To investigate the effects of weather conditions on outbreaks of Salmonella food poisoning, the relationships of five weather indices, i.e., daily maximum, minimum and mean temperatures and minimum and mean humidity with daily outbreaks of Salmonella (S.Enteritidis) food poisoning by causes (incriminated food), i.e., eggs, non-eggs, and unidentified, were examined by multiple logistic regression analysis, for the years of 1989-95 in Japan, using outbreak of food poisoning as a dependent variable and five weather indices asindependent variables. During this period, the type of Salmonella detected in food poisoning cases was reported to be mainly Salmonella . Enteritidis, whereas Salmonella Typhimurium had been frequently found in the preceding years. The following results were obtained: (1) Salmonella food poisoning caused by eggs had positive relationships to the minimum temperature on the day of its outbreak and of one day before, and to the mean temperatures of two and three days before; (2) poisoning due to non-egg foods had positive relationships to the minimum temperatures of the outbreak day and of one, two, and three days before; (3) poisoning due to unidentified cause had positive relationships to the mean temperatures of the outbreak day and of one day before, and to the minimum temperatures of two and three days before. Increase in 1°C of the mean or minimum temperatures resulted in 7.2-12.2% increase in the risk of outbreak. It is thus suggested that high temperatures lead to outbreaks of Salmonella food poisoning regardless of the causative food for the years of 1989-95 in Japan, possibly due to the change in type of Salmonella.