Norovirus cases surging in parts of U.S.

Some places in the U.S. are seeing an uptick in cases of the stomach bug known as norovirus. 

The U.S. Centers for Disease Control and Prevention says there were 91 outbreaks reported during the week of Dec. 5, up from 69 cases the last week of November, per The Associated Press. There have been a maximum of 65 outbreaks reported during the first week of December in recent years.

The highly contagious infection is the leading cause of foodborne illness and causes sudden vomiting and diarrhea. Other symptoms include nausea, stomach pain, body ache, headache and fever. There is no medication to treat it. 

According to the CDC, there are between 19 million to 21 million cases of norovirus a year, and an estimated 900 people die from it while 109,000 are hospitalized. It's estimated that one in every 15 people per year are infected. 

Norovirus is often seen on cruise ships, nursing homes, jails, schools and crowded living conditions. Cases are usually highest between November to April in the U.S. 

Experts have said masking doesn't offer much help to prevent norovirus, since it is spread through direct contact with an infected person, surface, or food and water — not through air. 

They recommend handwashing with soap and water, drinking clean water and paying attention to food safety regulations. Infected people usually start feeling better in about one to three days.