The Epidemiology of Foodborne Botulism Outbreaks: A Systematic Review

We performed a systematic review of foodborne botulism outbreaks to describe their clinical aspects and descriptive epidemiology in order to inform public health response strategies. We searched seven databases for reports of foodborne botulism outbreaks published in English from database inception to May 2015. We summarized descriptive characteristics and analyzed differences in exposure and toxin types by geographic region. We performed logistic regression to assess correlations between exposure source, implicated food, and outbreak size. There were 197 outbreaks reported between 1920 and 2014. The median number of cases per outbreak was 3 (range 2-97). The majority of reported outbreaks (109; 55%) occurred in the United States. Toxin types A, B, E, and F were identified as the causative agent in 34%, 16%, 17%, and 1% of outbreaks, respectively. The median duration between exposure and symptom onset was approximately 1 day. The mean percentage of cases requiring mechanical ventilation per outbreak was 34%. Seventy percent of all outbreaks and 77% of small outbreaks (≤11 cases) originated from point source exposures, while commercial foods were significantly (odds ratio, 6.9; 95% confidence interval, 2.2-21.1) associated with large outbreaks (≥12 cases). Toxin type A accounted for half of outbreaks, and these outbreaks had a higher proportion of patient ventilatory failure. Most outbreaks were due to point source exposures, while outbreaks due to commercial food were larger. For effective responses to foodborne botulism outbreaks, these findings demonstrate the need for timely outbreak investigation and hospital surge capacity.