Noroviruses: Widespread and Easy to Catch

Most of us have experienced one of those weird intestinal illnesses that make us miserable for a few days - with stomach cramps, headache, fever, and vomiting - and then disappear mysteriously. Researchers are now finding out that many of these illnesses are caused by a group of viruses called noroviruses.

Noroviruses cause gastroenteritis, the inflammation of the stomach and intestines sometimes misnamed "stomach flu."

The main viruses that cause gastroenteritis used to be called "Norwalk-like viruses" because Norwalk is the most well-known virus in this group. Now the viruses are referred to as noroviruses. Interest in the noroviruses is growing as researchers learn how often they make people sick - they have recently been implicated in outbreaks on military and cruise ships and in hotels, restaurants, daycare centers, nursing homes, and hospitals.

Noroviruses are very contagious. They usually are found in contaminated food or drinks, but they can also live on surfaces or be spread through contact with an infected person. Every year in the United States, 23 million norovirus infections result in an estimated 50 thousand hospitalizations and 310 deaths, according to the Centers for Disease Control and Prevention (CDC). Fortunately, people usually recover from noroviruses in 24 to 72 hours.

Where Do the Viruses Come From?
Noroviruses are transmitted when people consume food or water contaminated with feces from an infected person. You might think you don't have much contact with feces unless you're doing something like changing diapers, but fecal-oral contamination can occur when people involved in food preparation don't properly wash their hands or the food prep area. Shellfish such as oysters and clams often become contaminated via infected fecal matter from sick food handlers, or by the practice of some harvesters and recreational boaters of dumping raw sewage overboard.

These viruses are easily spread from person to person, and because we don't become immune to them, people can get the illnesses again and again.

Other foods associated with outbreaks have been linked to cold-prepared, ready-to-eat foods such as salads, coleslaw and sandwiches. Outbreaks have also been connected to drinking water and recreational water from pools, ponds or lakes where swimmers could have ingested water contaminated with feces from an infected person.

Unfortunately, there usually isn't any way to tell if someone is preparing your food with contaminated hands. Try to eat only well-cooked foods when eating away from home.

Symptoms of Norovirus Infection
The most common symptoms of infection with the Noroviruses are nausea with vomiting, diarrhea, and cramps. These symptoms occur in all age groups, although diarrhea is more common among adults and vomiting is more common in children. Many people also experience headache, fever, chills and muscle aches. The symptoms usually appear within 24 to 48 hours after exposure to the virus, but might appear any time from 10 to 50 hours after exposure. People are infectious (and able to spread the disease) as long as symptoms are present, and up to four days after diarrhea has stopped.

Prevention
Thorough handwashing following toilet use and prior to handling food is the best way to prevent the spread of these viruses. People who are already ill should never prepare food for anyone else. In addition, those currently ill with diarrhea or vomiting should not work in day care centers or care for patients in a health care facility until their symptoms have stopped.

Rest and Fluids
Illnesses caused by Noroviruses have no specific treatment. You should rest and drink plenty of fluids to make sure you don't become dehydrated. Infants, young children, and people who are unable to care for themselves, such as the disabled or elderly, are especially at risk for dehydration from loss of fluids.

This article includes information from the Wisconsin Department of Health and Family Services and the National Institute of Allergy and Infectious Diseases.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.