Norovirus (formerly called Norwalk-like Virus)
What are noroviruses?
Noroviruses are a group of viruses that can cause vomiting and diarrhea.
Where are noroviruses found?Infected humans are the only known source of this group of viruses. Anyone can get these infections.
How are the viruses spread?The viruses primarily are spread by direct contact with vomitus (including airborne particles) or feces from an infected person and then transferring the virus to the mouth from the hands. This type of spread is a common cause of outbreaks in institutions such as nursing homes. In addition, food may be contaminated by infected food handlers who fail to thoroughly wash their hands after using the bathroom. Outbreaks also have occurred due to consumption of raw or undercooked oysters harvested from fecally contaminated waters. Cooking kills the virus. Drinking water contaminated by sewage can be a source of these viruses, as well.
What are the symptoms of norovirus illness?The major symptoms are vomiting and/or watery diarrhea. Other symptoms include nausea and stomach cramps. A low-grade fever occurs in about half of cases.
Can noroviruses cause severe problems?Most people recover on their own within 24 to 48 hours. It can be a serious illness for persons who are unable to drink enough fluids to replace what they lose through vomiting or diarrhea. Infants, young children, and persons who may be unable to care for themselves, such as the disabled or elderly, are at risk for dehydration from loss of fluids. Persons who are immunocompromised are at risk for dehydration because they may get a more serious illness, with greater vomiting or diarrhea. On rare occasions, deaths have been reported in nursing home residents.
How soon after exposure do symptoms appear?Symptoms usually start within 24 to 48 hours after exposure.
How long can an infected person spread noroviruses?An infected person can spread the virus for three days or more after diarrhea or vomiting stops.
Do infected people need to be excluded from school or work?Since the virus is passed in the feces, children in daycare, health care workers, or people who handle food should not go to school or work while they have diarrhea. Persons who work in nursing homes, take care of patients, or handle food should stay out of work for at least three days after symptoms subside.
What is the treatment for norovirus illness?There is no specific treatment. Persons with diarrhea and/or vomiting should drink plenty of liquids to prevent dehydration. Medications, including antibiotics (which have no effect on viruses) and other treatments, should be avoided unless specifically recommended by a physician.
To prevent norovirus illness:· Wash your hands frequently.· Promptly disinfect contaminated surfaces with household chlorine bleach-based cleaners.· Wash soiled clothing.· Avoid food or water from sources that may be contaminated.· Cook oysters completely to kill the virus.
Prepared by the Virginia Department of Health, January 2003