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
What Are the Symptoms of WNV?
BR WNV affects the central
nervous system. Symptoms vary.
- 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
- Milder Symptoms in Some
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.
- 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?
- 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
- 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
- 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?
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
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.
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.
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 breast milk
is still being evaluated. Talk with your care provider is you
What Can I Do to Prevent WNV?
The easiest and best way
to avoid WNV is to prevent mosquito bites.
- When you are outdoors, use insect repellents
containing DEET (N, N-diethyl-meta-toluamide). Follow
the directions on the package.
- 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
- Make sure you have good screens on your
windows and doors to keep mosquitoes
- Get rid of mosquito breeding sites by
emptying standing water from flower pots, buckets and
barrels. Change the water in pet dishes and replace the
water in bird baths 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
For additional information on West Nile Virus
please visit the Center for Disease Control website