Health officials say the Norwalk virus caused dozens of people at Sparrow's Dimondale nursing home to experience nausea, vomiting and severe diarrhea.

Health officials say an outside source probably brought the virus into the nursing home. Investigators say the virus was not related to mass food or water contamination, and they say it spread quickly because the nursing home residents were living in such close quarters.

Experts say the virus only lasts a couple days, and it's not life threatening. They do say people can prevent themselves from getting sick by thoroughly washing their hands.

wilx.com: Extended Web Virus

Norwalk Virus

• The Norwalk virus infection is an intestinal illness that often occurs in outbreaks.

• Norwalk and Norwalk-like viruses are increasingly being recognized as leading causes of food borne disease in the United States.

• The viruses are passed in the stool of infected persons. People get infected by swallowing stool-contaminated food or water. Outbreaks in the United States are often linked to raw oysters.

• Infected people usually recover in 2 to 3 days without serious or long-term health effects.

Protecting yourself from the Norwalk Virus.

• Wash hands with soap and warm water frequently. Always wash after visits to the washroom and before preparing or eating food.

• Cook all shellfish thoroughly before eating.

• Always wash raw vegetables before eating.

• Dispose of sewage in a sanitary manner.

Where does the virus come from and who is at risk?

• The virus was first identified in 1972 after an outbreak of gastrointestinal illness in Norwalk, Ohio.

• Norwalk and Norwalk-like viruses are found worldwide.

• Anyone can get Norwalk virus infection, but it may be more common in adults and older children.

Symptoms of Norwalk Virus infection.

• Nausea, vomiting, diarrhea, and stomach cramps.

• Severe illness or hospitalization is uncommon.

• No specific treatment is available. Persons who are severely dehydrated might need rehydration therapy.

Source: The Association of State and Territorial Directors of Health Promotion and Public Health Education’s (ASTDHPPHE) Web site contributed to this report (www.astdhopphe.org).