Gastrointestinal illness caused by norovirus has been making news the past week, with well-publicized outbreaks in the United Kingdom and New York City, but Idaho is not experiencing more cases than we would expect. We typically see increases in illness due to norovirus during the winter months.

The number of norovirus cases reported during December 2022 through January 2023 is about what we would expect based on the number of cases reported in previous years. Idaho had 48 cases reported during December 2022 through January 2023. By comparison, case counts during December and January in previous winters ranged from a low of 26 to a high of 77.

With or without high case rates, however, norovirus causes a nasty illness that’s best avoided, if possible.

How common is norovirus?

Norovirus tends to be thought of as a cruise ship illness because outbreaks on ships sound like a terrible vacation – and that’s when the media tends to cover it most. But for most of us, there’s a better chance of becoming infected in common public places such as restaurants or big events and in places where people gather and share bathrooms, such as nursing homes, day cares, schools, and camps.  It’s so highly contagious – a very small amount of the virus can make you sick. Norovirus is the most common cause of gastroenteritis in the United States, and the leading cause of foodborne illness. The Centers for Disease Control and Prevention estimates that 19 to 21 million cases of acute gastroenteritis are caused by norovirus each year.

What does norovirus do to us?

It’s not pleasant. Norovirus causes inflammation of the stomach and intestines. That leads to stomach cramping, nausea, vomiting, and diarrhea. The virus is found in the vomit and stool of infected people. Other symptoms include stomach pain, fever, headache, and body aches. Some people call it the “stomach flu,” but it is not related to influenza virus.

Who is at risk?

Everyone is at risk, but the very young and old and those with chronic conditions are more likely to get sick. It’s estimated that on average,  a person will get norovirus five times in their life.

Most people recover in about three days, but the virus causes up to 70,000 hospitalizations and up to 800 deaths a year in the United States.

How does a person become infected?

Norovirus is very infectious and easily spread. You can become infected  through contaminated drinks and foods, touching contaminated surfaces, and through direct contact with infected people. Food and drinks become contaminated by infected food handlers, placing food on contaminated surfaces, or food being grown in or harvested with contaminated water. Any shared surface such as door handles, shopping carts, and light switches can become contaminated when an infected person doesn’t thoroughly wash their hands after using the bathroom. Having direct contact with or caring for someone who is infected is also a way the virus is spread.

How long are people contagious?

People are most contagious from when they start to feel sick until at least three days after they recover. Some people are contagious for even longer. That’s why it’s so important to stay home when you feel sick and always wash your hands after using the bathroom. If you think you have norovirus, see your doctor, but also make sure to drink plenty of fluids to avoid dehydration, which can set in quickly.

So how can we protect ourselves?

There is no vaccine to prevent norovirus or any medication to treat it. The best way to protect yourself is to wash your hands often, but especially after using the toilet or changing a diaper, and always before eating or preparing food.

Other ways to reduce the risk of infection include thoroughly washing fruits and vegetables, and cooking oysters and other shellfish thoroughly before eating them. Also, don’t prepare food for others while you are sick and for at least three days after you recover.

Potentially contaminated surfaces should be cleaned with a bleach-based cleaner or other disinfectant labelled as EPA-registered against norovirus. Any contaminated clothing or blankets also should be washed and dried.

• CDC norovirus website: www.cdc.gov/norovirus
• CDC National Outbreak Reporting System dashboard: https://wwwn.cdc.gov/norsdashboard/

Dr. Katheryn Turner is deputy state epidemiologist in the Division of Public Health. 

The Idaho Department of Health and Welfare is dedicated to strengthening the health, safety, and independence of Idahoans. Learn more at healthandwelfare.idaho.gov.