What are noroviruses? Noroviruses
are a group of related viruses that
affect the intestinal tract causing
gastroenteritis illness. This group of
viruses has been also referred to as
caliciviruses and Norwalk-like viruses.
These viruses are an important cause of
gastrointestinal illness throughout the
United States, including Illinois.
What are the
symptoms of noroviruses? Many of
the noroviruses cause similar symptoms
that usually occur between 24 hours and
48 hours after exposure. They include
nausea, vomiting, diarrhea, abdominal
pain, body aches, headache, tiredness
and low-grade fever. Symptoms typically
last 24 hours to 60 hours and subside on
their own. There are no known long-term
effects after recovery from this
infection.
How common is
norovirus infection? The U.S.
Centers for Disease Control and
Prevention estimates that at least half
of all foodborne outbreaks of
gastroenteritis can be attributed to
noroviruses. Some studies indicate that
more than 60 percent of the U.S.
population is exposed to one or more of
these viruses by the age of 50.
Noroviruses are highly contagious and
can spread easily from person to person.
How do people come
in contact with these viruses?
Humans are the only source for these
viruses. These viruses do not multiply
outside the human body. The viruses are
present in the feces of infected persons
and can be transmitted to others when
hands are not thoroughly washed after
having a bowel movement. When an
infected person who did not wash hands
after toileting handles food that is not
later cooked, others who eat the food
can become infected. Heating foods to
cooking temperatures kills these
viruses. People also can be infected by
drinking water contaminated by sewage
containing one of these viruses or by
consuming ice made from contaminated
water. Unless thoroughly cooked,
shellfish (such as oysters) harvested
from waters containing sewage can
transmit the viruses. These viruses also
are transmitted readily from person to
person when hands are not washed after
toileting. There is some evidence that
the viruses can be transmitted by
aerosolized vomitus or contact with
objects contaminated with fecal
material. |
How are these infections diagnosed?
Standard hospital laboratories and
commercial laboratories usually are not
equipped to detect noroviruses. The
specialized laboratories that can detect
these viruses perform tests on stool
specimens from an infected person to
detect the virus. In Illinois, only the
Illinois Department of Public Health's
laboratories have the capability to
confirm a diagnosis of one of these
viruses. This laboratory service is
reserved for testing a small number of
people associated with recognized
outbreaks and is not available for
testing individual cases of
gastrointestinal illness.
If I have had a
norovirus infection in the past, can I
get it again? Yes. It appears
that immunity following norovirus
infection varies from person to person.
It is possible some persons achieve
immunity but more studies are needed to
better understand susceptibility to
reinfection.
How can these
infections be prevented?
Food handlers should practice
careful handwashing after toileting and
before food preparation. Food handlers
should not have bare hand contact with
ice. Persons involved in food
preparation who have symptoms of
gastroenteritis should be restricted
from work until they no longer have
diarrhea. Water supplies should be
protected from the risk of contamination
by sewage. Plumbing in dwellings and
business establishments should be
constructed with no cross-connections to
prevent sewage from entering the
drinking water supply.
All persons can decrease their chance of
coming in contact with noroviruses by
following these preventive steps:
• Frequently wash your hands,
especially after toileting or changing
diapers and before eating or preparing
food.
• Carefully wash fruits and
vegetables, and steam oysters before
eating them.
• Thoroughly clean and
disinfect contaminated surfaces
immediately after an episode of diarrhea
or vomiting by using a bleach-based
household cleaner. If using liquid
household bleach prepared daily, one
part bleach to nine parts water (1:10
dilution) is recommended.
• Immediately remove and wash
clothing or linens that may be
contaminated with feces or vomitus (use
hot water and soap).
• Flush or discard any
vomitus and/or stool in the toilet and
make sure that the surrounding area is
kept clean.
• Persons who are infected
with norovirus should refrain from food
preparation while they have symptoms and
for three days after they recover from
their illness.
Outbreaks of norovirus in long-term care
facilities are not uncommon and are
frequently transmitted from person to
person (including residents, staff,
visitors and volunteers). Strict
compliance with good hygiene practices
is important to prevent the spread of
norovirus in this population. |
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