Declining Vibrio parahaemolyticus and Salmonella, Increasing Campylobacter and Persisting Norovirus Food Poisonings: Inference Derived from Food Poisoning Statistics of Japan

The annual number of outbreaks of Vibrio parahaemolyticus and Salmonella food poisoning and that of patients in Japan, from 2000 to 2018, decreased exponentially even though the size of the individual outbreaks (the number of patients per outbreak) tended to become larger. For food poisonings caused by Campylobacter, the annual number of outbreaks increased exponentially while outbreak size became smaller and the annual number of patients remained almost unchanged. For food poisoning caused by norovirus, both the number of outbreaks and that of patients remained high throughout. Over time, the geographical and seasonal distribution of food poisonings became narrower for Vibrio parahaemolyticus and Salmonella, while they became wider for Campylobacter and norovirus. Further analyses using the attack rate-patient number plots suggested that the number of the outbreaks was determined mainly by the levels of microbial contamination of foods before they were brought into the facilities for consumption.