Norovirus outbreaks reported on 3 cruise ships this month, sickening hundreds
There are about 2,500 reported norovirus outbreaks in the U.S. each year. Norovirus, which is sometimes called the "cruise ship virus," causes more than 90% of diarrheal disease outbreaks on cruise ships, according to the CDC. However, norovirus outbreaks on cruise ships account for only a small percentage of all reported norovirus outbreaks.