An outbreak of norovirus-related acute gastroenteritis associated with delivery food in Guangzhou, southern China

Abstract

Objectives Large numbers of students at a school located in Guangzhou city developed a sudden onset of symptoms of diarrhea and vomiting. In order to control the outbreak, an epidemiological investigation was conducted to determine the pathogen, sources of infection, route of transmission and risk factors. Methods The study population consisted of probable cases and confirmed cases. An active search was conducted for cases among all students, teachers and other staff members. A case control study was carried out using online standardised questionnaires. Data were obtained regarding demographic characteristics, gastrointestinal symptoms, personal hygiene habits, history of contact with a person with diarrhea and/or vomiting and dining place in the past 3 days. Rectal swabs or stool specimens of the cases, food handlers and environmental smear swab samples were collected to detect potential intestinal viruses and bacteria. Odds ratios (ORs) and 95% confidence intervals were calculated. Results A total of 157 cases fit the definition of the probable case, including 46 cases of laboratory-confirmed norovirus infection between March 8 and March 22, 2018. The proportion of the students who had eaten delivery food three days before the onset of disease in the case group was 2.69 times that in the control group (95%CI: 1.88-3.85). Intake of take-out food three days before, exposure to similar cases 72 hours before onset and case in the same dormitory were risk factors. A total of 20 rectal swabs samples from students, 10 rectal swabs from food handlers and 2 environmental swabs samples of out-campus restaurant were tested positive for norovirus (GⅡ). Conclusions The outbreak of norovirus infectious diarrhea was determined. Food handling practices carries potential risk of acute gastroenteritis outbreaks due to a lack of surveillance and supervision. More attention should be paid to the monitoring and supervision of food handlers to reduce the incidence of norovirus-related acute gastroenteritis associated with delivery food.