Disease
Fact Sheet Series:
What are noroviruses?
Noroviruses (previously called Norwalk viruses,
caliciviruses, or SRSVs) are a group of viruses that cause acute
gastroenteritis in humans, often referred to as "stomach flu".
However, noroviruses are completely unrelated to influenza, a respiratory
virus.
What are the symptoms of a norovirus infection?
The most common symptoms are a sudden onset of
vomiting, watery, non-bloody diarrhea, abdominal cramps, nausea and
headache. The symptoms occur in all age groups, but vomiting is more
common in children. Many persons may also experience low-grade fever,
headache, chills, muscle aches and fatigue.
How soon do symptoms appear?
The symptoms may appear from 12 to 60 hours after
exposure to the virus, but usually occur within 24 to 48 hours.
How are noroviruses spread?
The norovirus enters through the mouth, multiplies in
the body, and is passed in the highly infectious stool or vomit of an
infected person. If careful hand washing with soap is not done, the virus
can be carried on an infected person’s hands. If the infected person
then handles food or drink that someone else consumes, the virus can be
transmitted to others. Food associated outbreaks have been linked to cold
prepared, ready-to-eat foods (e.g., salads, coleslaw, sandwiches or
desserts) and shellfish harvested in contaminated waters. Outbreaks have
also been associated with drinking water and recreational water (e.g.,
swimming ponds and beaches) where persons may have ingested water
contaminated with fecal matter from an infected person.
Direct person-to-person contact or environmental
contamination (e.g., exposure to areas where fecal accidents or vomiting
has occurred) may also be a route of transmission.
How infectious are noroviruses?
Noroviruses are highly infectious and a very small
number of virus particles may result in symptomatic infections.
For how long is a person infectious?
The virus is very easily passed from person-to-person
from the time of symptom onset and up to 48 hours after diarrhea or
vomiting have stopped. In some cases the viruses may be shed for up to a
week.
What is the treatment for this illness?
There is no treatment for this illness. Most people
recover in two to three days after they become ill. Supportive treatment
such as fluid replacement may be needed to prevent dehydration in severe
cases.
What can be done to prevent the spread of noroviruses?
Thorough hand washing (See Division of Public Health
"Hand washing" Fact Sheet) following toilet use and before
handling food is the best way to prevent the spread of these viruses.
Persons currently ill with diarrhea or vomiting should not handle food,
work in day care centers or care for patients in a health care facility
until at least 48 hours after these symptoms have stopped.
For more information, contact your
Local
Public Health Department
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Last Revised: March 20, 2008
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