Norovirus Infection

Norovirus is a group of viruses that causes severe vomiting and diarrhea. It’s a very common illness and it’s very contagious. Norovirus outbreaks usually happen seasonally in colder months. The infection is the No. 1 cause of foodborne illness in the United States.

The first norovirus outbreak occurred in Norwalk, Ohio, USA, in a school in 1968. For this reason, the first strain of norovirus was known as the Norwalk virus.

What is the difference between norovirus and the stomach flu?

Norovirus causes gastroenteritis, which some people may call the “stomach flu.” The influenza virus causes respiratory flu, not gastroenteritis.

How many types of norovirus exist?

There are several different types (strains) of norovirus. It’s in the Caliciviridae family of viruses that cause inflammation of your stomach and intestines (gastroenteritis). In this family, there are 10 groups with 48 types. The most common type is GII.4.

How common is norovirus?

Norovirus is very common. Globally, about 685 million cases are reported each year. Of that estimate, over 200 million cases affect children.

Is norovirus seasonal?

Norovirus outbreaks occur most often between November and April in countries above the equator and between April and September in countries below the equator. There’s usually no specific season for outbreaks in areas on the equator.