A sharp increase in norovirus cases is sweeping the United States, according to the latest data from the Centers for Disease Control and Prevention (CDC). Often called the "stomach flu," norovirus is a leading cause of gastroenteritis,

According to the latest CDC data, there were 91 outbreaks of norovirus reported during the week of Dec. 5. During the last week of November, there were 69 outbreaks, The Associated Press reported. In Minnesota, more than 40 outbreaks were reported in December, according to that state’s Department of Health.

Outbreaks of the highly contagious stomach virus are more than double what they were last year at the time, CDC says. Protect yourself by washing hands with soap often — antibacterial gel doesn't work well against the virus.