Norovirus causes inflammation of the stomach or intestines or both. This is called acute gastroenteritis.  The most common symptoms are:

• diarrhea,
• vomiting (throwing up),
• nausea, and
• stomach pain.

Other symptoms include:

• fever,
• headache, or
• body aches.

A person usually develops symptoms 12 to 48 hours after being exposed to norovirus. Most people with norovirus illness get better within 1 to 3 days.

If you have norovirus illness, you can feel extremely ill and throw up or have diarrhea many times a day. This can lead to dehydration, especially in young children, older adults, and people with other illnesses.

Symptoms of dehydration are decrease in urination, dry mouth and throat, and feeling dizzy when standing up.  Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy.

Norovirus is a highly contagious virus.  Anyone can get infected with norovirus and get sick.  Also, you can get norovirus illness many times in your life.  One reason for this is that there are many different types of noroviruses.  Being infected with one type of norovirus may not protect you against other types.

Norovirus can be found in your stool (feces) even before you start feeling sick.  The virus can stay in your stool for 2 weeks or more after you feel better.

You are most contagious:

• when you are sick with norovirus illness, and
• during the first few days after you recover from norovirus illness.

You can become infected with norovirus by accidentally getting stool or vomit from infected people in your mouth. This usually happens by:

• eating food or drinking liquids that are contaminated with norovirus,
• touching surfaces or objects contaminated with norovirus then putting your fingers in your mouth, or
• having contact with someone who is infected with norovirus (for example, caring for or sharing food or eating utensils with someone with norovirus illness).

Norovirus can spread quickly in closed places like daycare centers, nursing homes, schools, and cruise ships. Most norovirus outbreaks happen from November to April in the United States.