Noroviruses Leave a Calling Card --- Again

A mass outbreak of sickness in the College Park, Md., area last month is the most recent reminder of a generally harmless but nonetheless highly contagious group of viruses often associated with stomach flu.

Right: Image courtesy of Iowa State University's Food Safety Project.

Noroviruses, as the viruses are now commonly known, are different from bacteria and parasites, some of which can cause similar symptoms.

“The difference is size,” says Dr. Jean Weese, an Alabama Cooperative Extension System food scientist and Auburn University associate professor of nutrition and food science. “Viruses are smaller, much smaller than parasites and bacteria and aren’t affected by treatment with antibiotics.”

Symptoms associated with noroviruses are typically, though inaccurately, identified as stomach flu. Noroviruses, however, aren’t related to the flu, a respiratory illness caused by a different virus, Weese says.

The good news is that symptoms associated with noroviruses usually aren’t serious or lasting, though this makes them no less unpleasant. Vomiting and diarrhea are associated with most norovirus cases, though children typically experience more vomiting than adults.

“Most people recover in about 2 or 3 days and suffer no long-term health problems,” Weese says. “On the other hand, some people --- especially immune-compromised individuals such as the very young and very old --- run the risk of dehydration if they can’t drink liquids fast enough to replace what they’ve lost from diarrhea and vomiting.”

Seriously dehydrated people should seek immediate medical attention, she says.

Symptoms associated with noroviruses usually occur within 24 to 48 hours following ingestion of the virus.

Noroviruses are extremely contagious and are typically spread by eating foods or drinking liquids contaminated with the virus. The viruses also can be spread hand to mouth after from touching contaminated surfaces or objects.

Human waste is the most common source of infection, which accounts for why feces-contaminated foods, particularly shellfish and water, are prime sources of the virus.

“Mollusks and any seafood that may have been contaminated with sewage or sewage-polluted water are major culprits,” Weese says.

Cooking of raw shellfish for a minimum of four minutes at 194 degrees F is effective against the virus, Weese says. She also advises thorough hand washing, especially in cases where someone is dealing with an infected person.

Individuals with noroviruses also should avoid preparing food while they have the symptoms and for three days after these symptoms disappear.

Weese also cites airborne contamination as another possible cause --- “most likely from surfaces contaminated with feces and vomit, even though this can’t be seen.”

Anyone can be infected by noroviruses, though some people are more genetically prone than others. Due to the large number of strains associated with noroviruses, it is very difficult to develop immunity.

Norovirus was linked recently to outbreaks affecting about 60 people in late August at a building in College Park, MD. A similar outbreak occurred earlier in the month nearby on the University of Maryland campus.

[Source: Dr. Jean Weese, Alabama Cooperative Extension System Food Scientist and Auburn University Associate Professor of Nutrition and Food Science, (334) 844-3269.]

Posted by Jim Langcuster at September 9, 2004 04:45 PM | TrackBack