Investigators from the Minnesota Department of Health are probing a norovirus outbreak that affected more than 60 students in the Renville County West school district last week. The students complained of vomiting and severe diarrhea. Noroviruses cause gastroenteritis, which is an inflammation of the stomach and the small and large intestines, in people of all ages, though it is most dangerous for young children, seniors and people with compromised immune systems.

The virus, which is readily spread, is becoming increasingly more common in Minnesota in recent months. Health investigators and school officials have been working diligently to control the norovirus outbreak and urge everyone with symptoms of the virus to remain at home so as not to further spread the illness.

The Centers for Disease Control and Prevention reports that some common ways to contract a norovirus infection include contaminated food and water, contact with an infected person or with surfaces contaminated by a person with the disease, and unwashed hands and dirty surfaces. Investigators are looking for the exact cause of the outbreak and have ruled out food as a possible source. In the meantime, measures are being taken to stop the spread of the illness in the school. Superintendent Lance Bagstad said the district will be using a bleach disinfectant, made by mixing ¼ cup bleach with one gallon of water, to sanitize every surface in the school building including disinfecting school bathrooms.

Noroviruses are resistant to disinfection because the virus is excreted in very large numbers, making it difficult for disinfectants to kill all of them before the reactive agent is used up. Evidence from outbreak investigations and laboratory-based research has shown that there are a limited number of disinfectants, such as chlorine bleach, that are effective against noroviruses. Bleach destroys these viruses by breaking their outside protein cover and genetic material into inactive fragments.

So how can one prevent a norovirus infection? Remember to wash hands with soap and warm water after using the bathroom, changing a diaper, blowing your nose, sneezing or coughing, caring for a sick person, playing with a pet, and also before preparing or eating raw or undercooked food. Cook all shellfish thoroughly and wash raw vegetables and fruits before eating. Food handlers should never contact ready-to-eat food with bare hands. Food preparation surfaces should be regularly disinfected using one tablespoon of bleach in one gallon of water. Solutions should be made fresh daily, and bleach solutions should never be mixed with ammonia-based cleaning products.

(Chris Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.)

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