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What Is West Nile Virus?
West Nile virus (WNV) is a potentially serious illness. Experts
believe WNV is established as a seasonal epidemic in North America
that flares up in the summer and continues into the fall. This fact
sheet contains important information that can help you recognize and
prevent West Nile virus.
What Can I Do
to Prevent WNV?
The easiest and best way to avoid WNV is to prevent mosquito bites.
See our other fact sheet
West Nile
Virus - How To Avoid Infection
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When you are outdoors, use insect repellents
containing DEET (N, N-diethyl-meta-toluamide). Follow the
directions on the package.
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Many mosquitoes are most active at dusk and dawn. Be
sure to use insect repellent and wear long sleeves and pants at
these times or consider staying indoors during these hours.
Light-colored clothing can help you see mosquitoes that land on
you.
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Make sure you have good screens on your windows and
doors to keep mosquitoes out.
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Get rid of mosquito breeding sites by emptying
standing water from flowerpots, buckets and barrels. Change the
water in pet dishes and replace the water in birdbaths weekly.
Drill holes in tire swings so water drains out. Keep children's
wading pools empty and on their sides when they aren't being
used.
What Are the
Symptoms of WNV?
WNV affects the central nervous system. Symptoms vary.
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Serious Symptoms in a Few People.
About one in 150 people infected with WNV will develop severe
illness. The severe symptoms can include high fever, headache,
neck stiffness, stupor, disorientation, coma, tremors,
convulsions, muscle weakness, vision loss, numbness and
paralysis. These symptoms may last several weeks, and
neurological effects may be permanent.
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Milder Symptoms in Some People.
Up to 20 percent of the people who become infected will display
symptoms which can include fever, headache, and body aches,
nausea, vomiting, and sometimes swollen lymph glands or a skin
rash on the chest, stomach and back. Symptoms can last for as
short as a few days, though even healthy people have been sick
for several weeks.
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No Symptoms in Most People.
Approximately 80 percent of people (about 4 out of 5) who are
infected with WNV will not show any symptoms at all.
How Does West
Nile Virus Spread?
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Infected Mosquitoes.
Most often, WNV is spread by the bite of an infected mosquito.
Mosquitoes are WNV carriers that become infected when they feed
on infected birds. Infected mosquitoes can then spread WNV to
humans and other animals when they bite.
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Transfusions, Transplants, and Mother-to-Child.
In a very small number of cases, WNV also has been spread
through blood transfusions, organ transplants, breastfeeding and
even during pregnancy from mother to baby.
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Not through touching.
WNV is not spread through casual contact such as touching or
kissing a person with the virus.
How Soon
Do Infected People Get Sick?
People typically develop symptoms between 3 and 14 days after they
are bitten by the infected mosquito.
How Is
WNV Infection Treated?
There is no specific treatment for WNV infection. In cases with
milder symptoms, people experience symptoms such as fever and aches
that pass on their own. In more severe cases, people usually need to
go to the hospital where they can receive supportive treatment
including intravenous fluids, help with breathing and nursing care.
What
Should I Do if I Think I Have WNV?
Milder WNV illness improves on its own, and people do not
necessarily need to seek medical attention for this infection though
they may choose to do so. If you develop symptoms of severe WNV
illness, such as unusually severe headaches or confusion, seek
medical attention immediately. Severe WNV illness usually requires
hospitalization. Pregnant women and nursing mothers are encouraged
to talk to their doctor if they develop symptoms that could be WNV.
What Is the
Risk of Getting Sick from WNV?
People over 50
at higher risk to get sick. People over the age of 50 are more likely to develop
serious symptoms of WNV if they do get sick and should take special
care to avoid mosquito bites.
Being outside means you're at risk. The more time you're outdoors, the more time you could be
bitten by an infected mosquito. Pay attention to avoiding mosquito
bites if you spend a lot of time outside, either working or playing.
Risk through medical procedures is very low. All donated blood is checked for WNV before being
used. The risk of getting WNV through blood transfusions and organ
transplants is very small, and should not prevent people who need
surgery from having it. If you have concerns, talk to your doctor.
Pregnancy and
nursing do not increase risk of becoming infected with WNV.
The risk that WNV may present to a fetus or an
infant infected through breastmilk is still being evaluated. Talk
with your care provider is you have concerns.
What Is
the CDC Doing About WNV?
CDC is working with state and local health departments, the Food and
Drug Administration and other government agencies, as well as
private industry, to prepare for and prevent new cases of WNV.
Some things CDC is doing include:
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Coordinating a nation-wide electronic database where
states share information about WNV
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Helping states develop and carry out improved mosquito
prevention and control programs
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Developing better, faster tests to detect and diagnose
WNV
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Creating new education tools and programs for the
media, the public, and health professionals
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Opening new testing laboratories for WNV
What
Else Should I Know?
If you find a dead bird: Don't handle the body with your bare
hands. Contact your local health department for instructions on
reporting and disposing of the body.
This is a CDC Fact Sheet
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