Norovirus in Montana

Norovirus is the most common cause of acute gastroenteritis in the United States, including Montana. About 87% of all gastroenteritis outbreaks are caused by norovirus, and 61% are laboratory confirmed. The greatest burden of these outbreaks affect senior care settings (68%), such as nursing homes and assisted living facilities, where vulnerable populations reside close together.

Similar to influenza, norovirus illnesses and associated outbreaks often occur during the winter season. In fact, 78% of outbreaks are reported from November through May. Norovirus outbreaks are reportable in Montana and when laboratory samples are available, they are tested to search for any new strains, as those can have a more severe impact on the general population. A new strain of norovirus emerged in March 2012 and has been the predominant strain (77%) in Montana since then.

What is Norovirus?

Noroviruses are the most common of the viruses that cause gastroenteritis. The usual symptoms of gastroenteritis include diarrhea, vomiting, nausea, and stomach pain. There is no specific treatment for this illness and most individuals recover in 1 to 3 days. The illness can last longer and be more severe in young children, older persons, or persons who have other health conditions.

How is Norovirus transmitted?

The virus is highly contagious and can spread rapidly. A person can become ill by ingesting the virus from contaminated food or water or by close contact with someone who is ill. Touching surfaces or objects that are contaminated with norovirus, and then transferring the virus hand to mouth is another common way of becoming infected.

How to prevent Norovirus infection? 

Follow the 5 main tips to prevent the spread of Norovirus:

  1. Practice proper hand hygiene: Wash your hands carefully with soap and water, especially after using the bathroom or changing diapers and always before eating or preparing food. Alcohol-based hand sanitizers are not a substitute for washing with soap and water.
  2. Take care in the kitchen: Carefully wash fruits and vegetables, and cook oysters and other shellfish thoroughly before eating them.
  3. Do not prepare food while ill: People who are infected with norovirus should not prepare food for others while they have symptoms and for 3 days after they recover from their illness.
  4. Clean and disinfect contaminated surfaces: After an episode of illness, such as vomiting or diarrhea, immediately clean and disinfect contaminated surfaces by using a bleach-based household cleaner as directed on the product label or a solution made by adding 5–25 tablespoons of household bleach to 1 gallon of water [Calculations based on 5.25% bleach concentration].
  5. Wash laundry thoroughly: Immediately remove clothing or linens that may be contaminated with vomit or fecal matter and wash with detergent at the maximum length available cycle, then machine dry. Handle soiled items carefully—without agitating them—to avoid spreading virus.

Review the DPHHS Norovirus Outbreak Management and Disease Prevention Guidelines for everyone.Video link to: Have you ever heard of norovirus?

Where can I learn more about norovirus?
Visit CDC’s norovirus website featuring factsheets, posters, videos, statistics and more. Please contact your local health department for questions and reporting issues.


Learn more about norovirus by clicking below on your area of interest and specialized guidance.

Currently, individual cases of norovirus illness are not reportable. However; health care providers should report all outbreaks of acute gastroenteritis, including suspected outbreaks of norovirus, to their local health department. Providers are encouraged to test ill patients symptomatic with acute gastroenteritis in an effort to notify jurisdictions early and help us detect outbreaks before they expand.

Most outbreaks of norovirus that are reported in the United States occur in healthcare facilities, including nursing homes and hospitals. In the previous four years, 72% out of all norovirus outbreaks in Montana were reported in health care settings such as long-term care facilities, assisted living facilities and hospitals. The greatest burden affects residents in nursing homes.

Norovirus is a leading cause of disease from contaminated foods in the United States. Foods that are most commonly involved in foodborne norovirus outbreaks include leafy greens (such as lettuce), fresh fruits, and shellfish (such as oysters). However, any food item that is served raw or handled after being cooked can become contaminated with noroviruses.

Outbreaks of norovirus illness have occurred in restaurants, cruise ships, schools, banquet halls, summer camps, and even at family dinners. These are all places where people often eat food handled or prepared by others. In fact, norovirus is the leading cause of illness from contaminated food in the United States. About 50% of all outbreaks of food-related illness are caused by norovirus.

Montana has adopted the "Food Code 2013, Recommendations of the United States Public Health Service, Food and Drug Administration". For certain communicable illnesses, additional restrictions may apply as outlined in   ARM 37.11.262  and  ARM 37.114.501

Anyone can be infected with norovirus and get sick. Also, you can have norovirus illness many times in your life. Norovirus illness can be serious, especially for young children and older adults. Montana regulations require that “children attending licensed daycares must be without vomiting and diarrhea for 24 hours before they return to the daycare facility”

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