Would you like norovirus with that? Investigation of two simultaneous outbreaks of foodborne viral gastroenteritis in Los Angeles County

Los Angeles County Department of Public Health (LACDPH) received reports of two clusters of gastroenteritis among patrons of several parties eating at two neighboring restaurants (Restaurants 1 and 2) on November 4th, 2007. Case finding was completed by compiling foodborne illness reports and using available reservation information for the dates in question. LACDPH interviewed patrons and employees from both restaurants 1 and 2 for food and medical history. Employees were additionally queried about food handling responsibilities and practices. LACDPH Environmental Health inspected the restaurants. Stool specimens were collected for viral study. Interviews were completed for 89 case patrons, 37 control patrons and 105 employees. Fruit salad and any salad bar item were identified as the likely vehicle at restaurant 1. Salads and desserts were identified as the likely source at restaurant 2. Environmental inspection revealed foodhandler A prepared desserts and salads at both restaurants while ill with diarrhea and vomiting with onset 12:00AM on 11/4/07. Laboratory testing confirmed norovirus in stools from 6 patrons and 5 employees, including foodhandler A. A second gastroenteritis cluster was identified on 11/14/07 among restaurant 2 patrons who dined on 11/10/07; foodhandler B from restaurant 2 was later identified as having similar symptoms with onset on 11/10/07. Foodhandler B primarily handled take-out orders and left work early on 11/10 because of illness. Adherence by supervisors to current California ill foodhandler requirements and fastidious food safety and handwashing practices by food workers could have prevented these outbreaks.