Cases of a wretched stomach bug are surging in parts of the United States this winter, according to government data. The most recent numbers from the US Centers for Disease Control and Prevention show there were 91 outbreaks of norovirus reported during the week of Dec.

But with 19 to 21 million illnesses each year in the United States, norovirus nevertheless causes on average 900 deaths and 109,000 hospitalizations annually, mostly among adults

Norovirus outbreaks are surging in the United States this winter, with 91 cases reported in early December, a significant rise from previous years, according to CDC data.

Norovirus is the leading cause of foodborne illness in the US, responsible for 58% of infections yearly. It spreads easily, with as few as 10 viral particles causing illness.