Recently, I was a substitute teacher at a local school. 

Over 100 students were called in sick, and several were sent home during the day. Yes, I did get sick later that evening, experiencing chills, fever, and intestinal problems.

The culprit: norovirus. 

Norovirus is the leading cause of foodborne illness outbreaks in the U.S., according to the Centers for Disease Control (CDC). Noroviruses are a group of viruses that cause acute gastroenteritis, or an inflammation of the lining of the stomach and intestines, resulting in nausea, vomiting, diarrhea, and abdominal cramps.

Annually, norovirus causes 19 million to 21 million cases of vomiting and diarrhea in the U.S., 465,000 emergency room visits, 109,000 hospitalizations, and 900 deaths, according to the CDC. 

Anyone can become infected with norovirus, which spreads year-round, but outbreaks are most common during winter. Norovirus is highly contagious; it only takes a few virus particles to cause infection.

It is spread primarily through the fecal-oral route: Bacteria or viruses shed in stool end up surfaces and our hands, and then get passed from our hands to our mouths, where they are ingested.

Norovirus may be transmitted directly from an infected person or indirectly through contaminated surfaces, objects, foods, or drinks.

If in close contact with someone with an active infection with norovirus, you are at high risk of getting it. Norovirus can spread by caring for an infected person, sharing utensils, or changing diapers.

Even if somebody throws up and there are droplets of vomit aerosolized in the air — that can cause infection. It takes minimal virus particles to transmit the disease, which is why norovirus causes so many explosive outbreaks.

According to the CDC, fewer than 100 norovirus particles can make you sick, and infected people typically shed billions of particles.

Most people are infectious from the time symptoms begin until about two or three days after symptoms resolve, but some people can remain contagious for up to two weeks after recovery. Outbreaks often occur in schools, daycares, healthcare settings, nursing homes, and cruise ships. 

According to the experts, norovirus’s most common signs and symptoms include vomiting, diarrhea, nausea, and stomach pain or cramps. Other possible symptoms include headaches, body aches, and a low-grade fever.

According to the CDC, norovirus symptoms usually develop within 12-48 hours after exposure. 

Norovirus usually lasts a few days. However, those at higher risk of developing severe or prolonged symptoms include babies, the elderly, and the immunocompromised.

If symptoms become chronic, this can lead to complications like dehydration. Replenish fluids lost from vomiting and diarrhea, which means drinking plenty of water, Pedialyte, or sports drinks.

Then, eat bland foods and try to let the virus pass through the body, which usually takes one to three days. Most people can be managed at home and should be isolated until they improve. 

However, it is essential to watch for signs of severe dehydration and to contact a healthcare provider. These include dry mouth, decreased urination, dizziness, and, in children specifically, crying without tears, fussiness, or unusual sleepiness.

Children under the age of 1, immunocompromised people, and those with prolonged or severe symptoms should also be seen by a physician. 

We do not have a vaccine against norovirus yet. However, there are steps you can take to prevent infection and transmission.

Hand hygiene is critical, but how you clean your hands matters: It must be with soap and water. Hand sanitizer does not work against norovirus; it is one of the few viruses that does not deactivate with alcohol.

Wash your hands after using the restroom or caring for someone with norovirus and before cooking and eating.

Use a high-level disinfectant like bleach when cleaning surfaces or objects contaminated with norovirus. If you or your child is sick, isolate to prevent the virus from spreading within the household.

It is essential to continue washing your hands often, even after you feel better.


Nancy J. Schaaf, a retired RN, worked as a school nurse, a nurse supervisor at a men’s prison, and a health educator. She earned her BSN at Edinboro University. She is a freelance writer whose health articles appear in magazines throughout the U.S. and Canada. She can be reached at

Have questions?

We are just a click away!