In Feb 09, a student in my daughter's class vomited once. Half of the students, included my daughter, in the same class got sick. They all had enterogastritis (腸胃炎). My daughter vomited over 5 times and had to be admitted to hospital. We thought she might die. In a few days, everyone in our house had 腸胃炎. I didn't know a virus can be transmitted so fast.