Norovirus Infection (cont.)

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What causes a norovirus infection? How are norovirus infections transmitted?

Infection occurs when humans inadvertently ingest material contaminated with small amounts of fluids or feces from an infected person. It only takes a small number of viruses to cause infection, so even microscopic amounts of feces or fluids can be contagious.

An infected person with vomiting or diarrhea can contaminate their environment directly or indirectly spread virus particles through aerosolized droplets when vomiting; however, the main route is by touching surfaces contaminated with the virus. Contamination may also occur in food and/or in water, which has led to infection spreading widely in restaurants or aboard cruise ships. Outbreaks in school systems occur regularly, sometimes spreading widely, as was the case with an outbreak in the Chicago public schools in 2010. The virus is very hardy and can live for days or weeks on surfaces, including clothing. Outbreaks often occur when groups of people congregate (for example, cruise ships, dormitories, schools, day-care centers).

What are norovirus infection symptoms and signs in adults, children, and babies?

Most people get sick within one day of ingesting norovirus (range 12-48 hours) so the virus has a short incubation period. Symptoms and signs include vomiting or watery diarrhea or both. Fever occurs in one-third to one-half of infected people. Cramping abdominal or stomach pain and a general feeling of tiredness, headache, and muscle aches are common.

People are usually thirsty, although they may have trouble keeping fluids down. In general, patients who can orally ingest about the same amount of fluid they lose through diarrhea, vomiting, or both do well. Symptoms in adults may be different than symptoms in children. Young children and babies may not complain of thirst but may appear listless or lethargic as they become dehydrated. Symptoms may be more severe in debilitated, elderly patients or pregnant patients. People who are unable to replace their fluids and develop signs of dehydration need medical care.

Most people have a mild illness that lasts two to three days. In contrast to bacterial diarrheas, such as those caused by Shigella or Campylobacter bacteria, norovirus does not cause blood or pus in the stool. The length of infection may be prolonged in patients who are in the hospital or in young children.

Norovirus has been associated with severe inflammation of the colon in newborns and with disease flares in children who have inflammatory bowel disease, but it is not yet clear what role norovirus is playing in these conditions.

Medically Reviewed by a Doctor on 9/27/2013

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