In July 2015, we investigated a foodborne illness outbreak in Sithalikuppam and Verupachi villages, Cuddalore district, Tamil Nadu, among the political rally attendees to determine the risk factors for illness. We conducted a retrospective cohort study, calculated risk ratio for the food exposures, and cultured stool specimens. Of 55 rally attendees, we identified 36 (65%) case patients; 32 (89%) had diarrhea and 20 (56%) had vomiting. Median incubation period was 14 h. Eighty-nine percent (32/36) of those who ate lemon rice at dinner had illness compared to 21% (4/19) of those who did not (RR 4.2). Of the six nonattendees who ate leftovers on July 25, all ate only lemon rice and became ill. Stool cultures were negative for Salmonella, Shigella, and Vibrio species. Lemon rice was probably contaminated with enterotoxins such as from Bacillus cereus. Our findings highlighted need for community food safety education and importance of thorough outbreak investigations.
Keywords: Acute diarrheal disease; Bacillus cereus; India; bacteria; foodborne outbreak.