OBJECTIVETo investigate the cause of an outbreak characterized by diarrhea and vomit in a middle school in Huzhou City.

METHODSComprehensive analysis was conducted based on field epidemiological study, clinical characteristics of the cases and laboratory test.

RESULTS578 cases of acute gastroenteritis were found. The attack rate was 23.58%. The most frequently observed clinical symptoms were diarrhea, vomiting, abdominal pain and nausea. Some few had fever. Most cases had slight clinical symptom with a course from 1 to 3 days. The cases were distributed in every class, showing no phenomenon of clustering. Norovirus were detected in 11 out of 15 stool samples by using RT-PCR. 6 were genogroup II norovirus. 3 were genogroup I norovirus. enogroup I and II norovirus were detected at the same time in 2 stool samples (the same student with 2 tests). Case-control study showed that drinking unheated bottled water was risk factor (OR = 2.46, 95% CI = 1.19-5.23), and had a dose response relation with the disease (chi = 24.8 P < 0.01). The epidemic was controlled soon through isolating patients during treatment, providing boiled water, disinfecting and health education.

CONCLUSIONThis was an infectious diarrhea outbreak caused by norovirus. The suspected transmission ways were drinking unheated bottled water and contact daily.

Acute Disease ; epidemiology ; Adolescent ; Caliciviridae Infections ; epidemiology ; virology ; Case-Control Studies ; Disease Outbreaks ; Female ; Gastroenteritis ; epidemiology ; virology ; Genotype ; Humans ; Male ; Norovirus ; classification ; genetics ; isolation & purification ; Water Microbiology ; Water Supply ; analysis