DPHHS Home       About Us       Contact Us       News & Events       Programs & Services       Health Data & Statistics

A - Z Index


Norovirus in Montana
Norovirus is the most common cause of acute gastroenteritis in the United States including Montana. Norovirus was the confirmed or suspected agent in the majority of outbreaks reported in Montana in previous years. Outbreaks often occur during the winter season. Sometimes when a new strain emerges, as it did in March 2012, there is an increase in outbreaks reported in that following season. The following graph illustrates the number of outbreaks that have been reported to the state health department over the years.

Norwalk Virus Graph

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.
  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.

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

Learn more about norovirus by clicking on select images for your area of interest and specialized guidance.
Health care providers Long term
care facilities
Food Handlers Schools/
Health care providers Long term care facilities Food handlers Schools/daycare

 Resources for Health Care Providers
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.

Figure 2: Setting of 1,518 Confirmed Norovirus Outbreaks, U.S., 2010-2011: Long-term Care Facility 59%; Restaurants 8%; Party and Event 6%; Hospital 4%; School 4%; Cruise Ship 4%; Other and Unknown 15%. Resources for long term care facilities and assisted living centers
Most outbreaks of norovirus that are reported in the United States occur in healthcare facilities, including nursing homes and hospitals. Nearly two-thirds of all norovirus outbreaks reported in the United States occur in long-term care facilities. Montana follows the national trend with 37 out of 55 outbreaks reported in healthcare facilities from 2010 through 2012.


 Resources for food handlers/restaurants
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.
In Montana, “no person, while infected with a disease in a communicable form that can be transmitted by foods or who is a carrier of organisms that cause such a disease or while afflicted with a (….) diarrheal illness or acute gastrointestinal illness (…) shall work in a food service establishment (…) [ARM 37.110.210]

 Resources for schools/ daycares
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” [ARM 37.95.139]