Noroviruses

Viral infections

More than half of foodborne illnesses in the US are viral. Most food borne viral infections have an incubation period of 1–3 days before the victim experiences symptoms. The symptoms are similar to those listed for bacterial infections. In healthy individuals, a foodborne viral illness is self-limiting; as the body rids itself of the infected food and the viral particles, the symptoms gradually resolve. One of the most common viral causes of foodborne illnesses are noroviruses, described below.

Noroviruses are a group of viruses that cause abdominal pain and cramping, nausea, and vomiting and diarrhea. Onset of symptoms is sudden, and can occur 12-48 hours after ingestion of the virus. Victims will often have flu-like symptoms of chills, fever, muscle aches, headaches, and feel very tired. Symptoms last one to two days, and during that time the victim may vomit repeatedly and feel very sick indeed.

Although seasonal flu may produce similar symptoms, noroviruses are distinct from seasonal stomach flu. They are transmitted by small particles of stool or vomit from an infected person. A major route of transmission is food that has come into contact with these particles. As with many other infectious agents that cause food poisoning, the best prevention is sound food handling and hygiene practices, especially washing of hands before touching food, and thorough cleaning of food preparation and cooking utensils, and of food preparation areas.

People working in hospitals, skilled nursing facilities, camps, child care centers, cruise ships, and other settings in which large numbers of people live in close proximity need to be especially concerned with hygiene when a member of their population develops a norovirus. The virus is highly communicable, and a person infected with norovirus is contagious from the time he or she starts feeling sick. The person remains contagious for three days after symptoms have resolved. Staff who contract norovirus should not be involved in food preparation or food service until three days after they have recovered.

Like other viruses, noroviruses are not affected by antibiotics. Treatment is supportive, encouraging bed rest, and providing sufficient fluids to replace those lost by vomiting and diarrhea. The principal complication of noroviruses is dehydration, the inability to replace the fluid volume lost. Young children and the elderly are most at risk for dehydration. Noroviruses are usually expelled from the body within two days. If symptoms persist, or if the victim is at risk for dehydration, be sure to consult your healthcare provider.