Hepatitis A Virus and Norwalk Virus

Viruses are the simplest organisms in nature. These microorganisms have been identified as causal agents in about 3 to 10 percent of foodborne illnesses. All foodborne viruses are transmitted via the oral-fecal route. In other words, they are shed in the feces and infect another person by being ingested in some way. The majority of infections are passed from person to person, or from a fecally soiled hand to the mouth, but other carriers include flies, soiled diapers, water, and food. Two of the most common viruses known to cause foodborne illnesses are the hepatitis A virus and the Norwalk virus.

Hepatitis A Virus

Hepatitis A infection occurs most frequently after contact with fecal matter. It is the only human hepatitis known to be transferred through fecally contaminated food and water, although hepatitis E has been suspected to have been associated with tainted drinking water. The hepatitis B virus is different in that it is transmitted through body fluids and not food. Polluted shellfish beds and vegetable fields have been reported as hepatitis A infection sources. Unlike most other meats and seafood, shellfish are eaten with their digestive tracts intact. Child-care centers are another possible source of contamination. Employees should always wash their hands after diaper changing and before handling food. Restaurant employees are also in a position to infect many.

An infected person can shed the virus for two weeks without showing any symptoms, which include prolonged fever, jaundice, abdominal pain, loss of appetite, fatigue, and darkened urine. The illness can occur 10 to 50 days after contact, and lasts from 2 weeks up to 6 months. A vaccine is available that is 95 percent effective against the virus.

Norwalk Virus

The Norwalk virus is spread via infected shellfish and food handlers, and by water containing raw sewage. Heating will destroy this virus, but freezing will not. People infected with the Norwalk virus experience headache, diarrhea, vomiting, abdominal pain, fever, and dehydration. The onset is within an hour or two of exposure, and recovery is usually fairly rapid. Norwalk virus infection outbreaks can be large.