(NEW YORK) -- Cases of norovirus appear to be on the rise in various parts of the U.S., according to data from the Centers for Disease Control and Prevention.
More than 90 norovirus outbreaks were reported during the week of Dec. 5, the most recent week for which data is available, according to the CDC.
CDC data from previous years for the same December week show a maximum of 65 outbreaks reported.
National CDC data reflects what has been reported in state and counties across the country.
In Minnesota, more than 40 outbreaks were reported in December, almost twice the usual number, according to the state Department of Health.
Earlier this month, an event celebrating the top restaurants in Los Angeles left at least 80 people sickened with norovirus, which was linked to raw oysters, the county's Department of Public Health confirmed to ABC News.
Norovirus is a highly contagious virus that is the most common cause of viral gastroenteritis, which is an inflammation of the inside lining of the gastrointestinal tract.
Although it's often referred to as the "stomach bug" or "stomach flu," norovirus illness is not related to influenza.
Norovirus is the leading cause of foodborne illness in the U.S., causing 58% of foodborne illnesses each year, according to the CDC.
The most common symptoms are nausea, vomiting, stomach pain and diarrhea. Patients, however, can also experience fever, headaches and body aches.
According to the federal health agency, every year the virus causes between 19 and 21 million illnesses, 109,000 hospitalizations and 900 deaths.
A person can become infected by having direct contact with someone who is infected and sharing food or utensils with them; touching surfaces or objects contaminated with norovirus and then touching their face or mouth; or consuming contaminated foods or liquids.
Typically, an infected person will develop symptoms between 12 to 48 hours after being infected. However, norovirus typically resolves quickly and, in most healthy adults, lasts one to three days, according to the CDC.
There is no specific medication or antiviral for norovirus, meaning the only treatment available is managing symptoms.
The CDC recommends staying hydrated and drinking liquids that replenish electrolytes, which can be depleted through diarrhea and vomiting.
Although symptoms will resolve in a few days for most people, certain groups are at high risk for severe dehydration including those under age 1, the elderly and the immunocompromised.
Health experts say the best way to prevent getting norovirus is to wash hands with warm soap and water for 20 seconds. Hand sanitizer does not work well against norovirus.
The CDC says people should wash their hands after using the toilet or changing diapers as well as when eating, preparing or handling food.
To prevent contamination from food, make sure fruits and vegetables are washed, and that shellfish is cooked to at least an internal temperature of 145 F.