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Noroviruses are a group of related viruses that affect the intestinal tract causing gastroenteritis illness. This group of viruses has been also referred to as caliciviruses and Norwalk-like viruses. These viruses are an important cause of gastrointestinal illness throughout the United States, including Illinois.
Many of the noroviruses cause similar symptoms that usually occur between 24 hours and 48 hours after exposure. They include the following:
Symptoms typically last 24 hours to 60 hours and subside on their own. There are no known long-term effects after recovery from this infection.
The U.S. Centers for Disease Control and Prevention estimates that at least half of all food-borne outbreaks of gastroenteritis can be attributed to noroviruses. Some studies indicate that more than 60 percent of the U.S. population is exposed to one or more of these viruses by the age of 50. Noroviruses are highly contagious and can spread easily from person to person.
Humans are the only source for these viruses. These viruses do not multiply outside the human body. The viruses are present in the feces of infected persons and can be transmitted to others when hands are not thoroughly washed after having a bowel movement.
When an infected person who did not wash hands after toileting handles food that is not later cooked, others who eat the food can become infected. Heating foods to cooking temperatures kills these viruses. People also can be infected by drinking water contaminated by sewage containing one of these viruses or by consuming ice made from contaminated water.
Unless thoroughly cooked, shellfish (such as oysters) harvested from waters containing sewage can transmit the viruses. These viruses also are transmitted readily from person to person when hands are not washed after toileting. There is some evidence that the viruses can be transmitted by aerosolized vomit or contact with objects contaminated with fecal material.
Food handlers should practice careful handwashing after toileting and before food preparation. Food handlers should not have bare hand contact with ice. Persons involved in food preparation who have symptoms of gastroenteritis should be restricted from work until they no longer have diarrhea.
Water supplies should be protected from the risk of contamination by sewage. Plumbing in dwellings and business establishments should be constructed with no cross-connections to prevent sewage from entering the drinking water supply.