Investigation of Norovirus-Induced Gastroenteritis Outbreak among Students in A High School

Donald Dah-Shyong Jiang

2008 Vol.24 NO.10

Correspondence Author： Donald Dah-Shyong Jiang

Abstract：

Outbreaks of norovirus-induced gastroenteritis have occurred on and off in Taiwan. On March 16, 2008, a norovirus-induced gastroenteritis outbreak occurred in A High School in Douliou City, Yunlin County. This investigation was conducted in order to understand the outbreak scale, transmission route, infection origin, possible causes of the outbreak, and to assess the effectiveness of the control and preventive measures. The investigation uses semi-structure questionnaires to collect information from the 12th grade students about disease symptoms and onset dates for the purpose of taking relevant specimens and determining the possible transmission route. In addition, a case-control study was conducted to explore the possibility of occurrence of food poisoning.
Among the 380 questionnaires distributed to the 12th grade students, a total of 138 cases fit the case definition showing an attack rate of 36.3%. Two fecal
specimens from student cases were tested positive for norovirus. Due to the fact that norovirus can be confirmed as the source of the infection, this episode can be determined as a norovirus-induced gastroenteritis outbreak. By examining the epidemic curve, we can also determine the transmission route to be of one-point common source infection. Three of the fecal specimens collected from the culinary staff were also tested positive for the same type and strain of norovirus (G2/4) as those of the infected students. After analysis of the lunch prepared by the school on March 15, it is evident that the tuna macaroni (OR=7.445, 95%CL = 2.571~21.554) is statistically linked to this norovirus-induced gastroenteritis outbreak. Therefore, the tuna macaroni is highly suspected to be the cause of this incident of food poisoning. Unfortunately, no food specimens were available to confirm this.
After the disinfection of the school’s kitchens, cafeteria, and surrounding environment, the school’s kitchen service was halted for a week. In addition, with the absence of the 3 infected culinary staff members, the enhancing of hand washing among the students, and other preventive measures taken, no new cases of vomiting and/or diarrhea occurred as of March 20. We suspected that this norovirus-induced gastroenteritis outbreak was induced by contaminated food. Therefore, it is recommended that corresponding health departments not only needs to carry out the regulation of retaining school lunches for 48 hours, but also to add new testing categories (e.g. norovirus) for the leftover food.
Keyword: norovirus, gastroenteritis, epidemiology, food posioning