Table 1.

Summary of the outbreaks.

Schools involved
Total number of schools	60
Basic characteristics of the epidemics
Total number of students and employees	45,878
Total cases	959 (2.1%)
Median attack rate	2.68%
Total student cases	949 (99.0%)
Total employee cases	10 (1.0%)
Male cases	500 (52.1%)
Female cases	459 (47.9%)
Interval between the first and last cases in days	3.5 ± 1.9
Primary symptoms
Cases with vomiting	914 (95.3%)
Cases with nausea	444 (46.3%)
Cases with abdominal pain	279 (29.1%)
Cases with fever	160 (16.7%)
Cases with diarrhoea	100 (10.4%)
Investigation of the transmission source and route
Samples of the transmission routes; positive/total samples	6/542 (1.1%)
Inadequacies in disease control and prevention
Incomplete disinfection of vomitus	44/60 (73.3%)
Lack of timely isolation	37/60 (61.7%)
Incomplete daily disinfection	31/60 (51.7%)
Lack of sanitary facilities, such as hand washing stations	9 (15.0%)
Mismanagement of public drinking water	1 (1.7%)

Categorical data are presented as frequencies with percentages; intervals between the first and last cases are presented as mean ± standard deviation. The overall rate was calculated by dividing the total cases by the total number of students and employees (959/45,878 = 0.021). The other rates were calculated by dividing each frequency by the appropriate denominator.