It spreads rapidly and virtually everyone will get it at least once in their lifetime.
Right now, we're in the middle of stomach flu season. Eighty percent of outbreaks happen between November and April.
But researchers are working on a new way to protect you and your family from the awful illness.
Lou Baxter has the story.
Heidi Button, had Norovirus, said: "It was the worst sickness I think I've ever had."
Every year, it infects 21-million Americans, sending 70 thousand to the hospital and killing 800. Norovirus, better known as the stomach flu, hit Heidi Button hard.
Heidi: "I literally slept on my bathroom floor all night and didn't move."
It causes nausea, vomiting and diarrhea. Infectious Disease Specialist, John Treanor says even when you feel better, you're still very contagious.
John Treanor, MD, University of Rochester Medical Center said: "Although you recover quickly, you continue to shed it from your body for many, many days afterwards, and it only takes the tiniest dose to infect the next person."
Early studies of a nasal vaccine for the stomach flu showed promise, but not as much as expected.
Treanor and his team are now testing an injectable vaccine in people.
John Treanor: "What we've seen with the injectable vaccine is that the antibody levels that are generated are much higher than we're seeing with the nasal vaccine."
Heidi says she would rather the needle stick than being violently sick.
Heidi: "It's a horrible virus."