The Centers for Disease Control and Prevention is warning Americans of a nationwide spike in norovirus outbreaks.

"It's the most common foodborne illness in the United States," says Dr. Jo-Anne Passalaqua, infectious disease specialist at Hartford Healthcare St. Vincent's Medical Center.

Norovirus, more commonly known as the stomach flu or stomach bug, is a contagious virus passed on by contact.

"Commonly associated with contact with sick people, eating or drinking contaminated food or contact with surfaces that people who have been ill have touched," Passalaqua says.

Symptoms usually include vomiting and diarrhea, which typically last for one to three days but people can sometimes carry the virus for as long as two weeks after recovery.

"Particularly in the setting of an outbreak, it means that food products may be contaminated, or surfaces may be contaminated, so we need to be all the more vigilant when we are out and about," Passalaqua advises.

She says the best way to decrease infection is by washing hands thoroughly with soap and water because "hand gels don't work very well towards this virus."

The CDC recommends staying home at least two days after symptoms have stopped.