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What
are noroviruses?
Noroviruses
are a group of viruses that cause the “stomach flu,” or gastroenteritis
(GAS-tro-en-ter-I-tis), in people. The term norovirus was recently approved
as the official name for this group of viruses. Several other names have
been used for noroviruses, including:
- Norwalk-like
viruses (NLVs)
- caliciviruses
(because they belong to the virus family Caliciviridae)
- small
round structured viruses.
Viruses
are very different from bacteria and parasites, some of which can cause
illnesses similar to norovirus infection. Like all viral infections, noroviruses
are not affected by treatment with antibiotics, and cannot grow outside
of a person’s body.
What
are the symptoms of illness caused by noroviruses?
The symptoms
of norovirus illness usually include nausea, vomiting, diarrhea, and some
stomach cramping. Sometimes people additionally have a low-grade fever,
chills, headache, muscle aches, and a general sense of tiredness. The
illness often begins suddenly, and the infected person may feel very sick.
In most people the illness is self-limiting with symptoms lasting for
about 1 or 2 days. In general, children experience more vomiting than
adults.
What
is the name of the illness caused by noroviruses?
Illness
caused by norovirus infection has several names, including:
- stomach
flu – this “stomach flu” is not
related to the flu (or influenza), which is a respiratory illness caused
by influenza virus.
- viral
gastroenteritis – the most common name for illness caused by norovirus.
Gastroenteritis refers to an inflammation of the stomach and intestines.
- acute
gastroenteritis
- non-bacterial
gastroenteritis
- food
poisoning (although there are other causes of food poisoning)
- calicivirus
infection
How
serious is norovirus disease?
People may feel very sick and vomit many times a day, but most people
get better within 1 or 2 days, and they have no long-term health effects
related to their illness. However, sometimes people are unable to drink
enough liquids to replace the liquids they lost because of vomiting and
diarrhea. These persons can become dehydrated and may need special medical
attention. This problem with dehydration is usually only seen among the
very young, the elderly, and persons with weakened immune systems.
How
do people become infected with noroviruses?
Noroviruses
are found in the stool or vomit of infected people. People can become
infected with the virus in several ways, including:
- eating
food or drinking liquids that are contaminated with norovirus;
- touching
surfaces or objects contaminated with norovirus, and then placing their
hand in their mouth;
- having
direct contact with another person who is infected and showing symptoms
(for example, when caring for someone with illness, or sharing foods
or eating utensils with someone who is ill).
Persons
working in day-care centers or nursing homes should pay special attention
to children or residents who have norovirus illness. This virus is very
contagious and can spread rapidly throughout such environments.
When
do symptoms appear?
Symptoms
of norovirus illness usually begin about 24 to 48 hours after ingestion
of the virus, but they can appear as early as 12 hours after exposure.
Are
noroviruses contagious?
Noroviruses
are very contagious and can spread easily from person to person. Both
stool and vomit are infectious. Particular care should be taken with young
children in diapers who may have diarrhea.How
long are people contagious?
People infected
with norovirus are contagious from the moment they begin feeling ill to
at least 3 days after recovery. Some people may be contagious for as long
as 2 weeks after recovery. Therefore, it is particularly important for
people to use good handwashing and other hygienic practices after they
have recently recovered from norovirus illness.
Who
gets norovirus infection?
Anyone can
become infected with these viruses. There are many different strains of
norovirus, which makes it difficult for a person’s body to develop
long-lasting immunity. Therefore, norovirus illness can recur throughout
a person’s lifetime. In addition, because of differences in genetic
factors, some people are more likely to become infected and develop more
severe illness than others.
What
treatment is available for people with norovirus infection?
Currently,
there is no antiviral medication that works against norovirus and there
is no vaccine to prevent infection. Norovirus infection cannot be treated
with antibiotics. This is because antibiotics work to fight bacteria and
not viruses.
Norovirus
illness is usually brief in healthy individuals. When people are ill with
vomiting and diarrhea, they should drink plenty of fluids to prevent dehydration.
Dehydration among young children, the elderly, the sick, can be common,
and it is the most serious health effect that can result from norovirus
infection. By drinking oral rehydration fluids (ORF), juice, or water,
people can reduce their chance of becoming dehydrated. Sports drinks do
not replace the nutrients and minerals lost during this illness.
Can
norovirus infections be prevented?
You can
decrease your chance of coming in contact with noroviruses by following
these preventive steps:
- Frequently
wash your hands, especially after toilet visits and 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 illness by using a bleach-based household cleaner.
- Immediately
remove and wash clothing or linens that may be contaminated with virus
after an episode of illness (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 not prepare food while they have
symptoms and for 3 days after they recover from their illness (see food
handler information sheet). Food that may have been contaminated by
an ill person should be disposed of properly.
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This page last modified on May 28, 2008
Content on this
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