Norwalk-like+virus

These viruses, also known as small round structured viruses or caliciviruses, are an important cause of gastrointestinal illness throughout the United States, including Illinois. Members of this category of viruses, subsequently referred to as Norwalk-like viruses, are typically named for the location in which they were first identified, for example, Hawaii, Snow Mountain, Montgomery County and Oklahoma. The Norwalk virus is the prototype for this group of viruses – there are at least 11 other related viruses – hence the name “Norwalk-like virus.”

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 food that is not later cooked is handled by an infected person who did not wash hands after toileting, 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 vomitus.

The signs and symptoms of Norwalk-like viruses are similar and usually occur between 24 hours and 48 hours after exposure. They include nausea, vomiting, diarrhea, abdominal pain, muscle aches, headache, tiredness and low-grade fever. Symptoms typically last 24 hours to 48 hours and subside on their own. There are no known long- term effects after recovery from this infection.

Norwalk and Norwalk-like viruses are increasingly being recognized as leading causes of foodborne disease in the United States. However, since no routine diagnostic test is available, the true prevalence is not known. Norwalk and Norwalk-like viruses have been linked to outbreaks of intestinal illness on cruise ships and in communities, camps, schools, institutions, and families.Many oyster-related outbreaks of intestinal illness linked to Norwalk-like viruses have been reported in Louisiana, Florida, Maryland, and other states where oyster harvesting is common. In 1993, 73 people in Louisiana and about 130 others in the United States who ate oysters from Louisiana became ill. A malfunctioning sewage system was the cause of an outbreak in 1996. An outbreak in 1997 was linked to sewage from oyster-harvesting boats.

Food handlers should practice careful handwashing after having a bowel movement, especially when handling food that will not be cooked later. 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.