What is West Nile virus?
West Nile virus is a virus commonly found in Africa,
West Asia, and the Middle East. It is carried by
mosquitoes. West Nile can cause disease in humans,
birds, horses, and some other mammals. The virus
was found in the U.S. in 1999 and in Utah in August
How do people get West Nile virus?
• By far, the most common way is through the
bite of an infected mosquito. That’s why prevention
• Very rarely it can be transmitted by:
• Blood transfusion or transplant
• Mother to baby (no baby has died)
• Lab workers through a needlestick (bird
sample not human)
Is there a vaccine available
to protect humans from West Nile virus?
No. Currently there is no West Nile virus vaccine
available for humans. Many scientists are working
on this issue, and there is hope that a vaccine
will become available in the next few years.
Who gets West Nile virus?
Anyone who is bitten by an infected mosquito can
get the disease. Persons over the age of 50 or those
with poor immune systems are more likely to develop
a serious illness if they are infected.
How does the disease spread?
Wild birds can carry West Nile virus, and the virus
is spread to birds by mosquitoes. Infected mosquitoes
can give West Nile virus to humans or other animals
while biting them. Not all mosquitoes carry West
Can you get West Nile virus
from another person or animal?
No. There is no proof that West Nile virus can be
passed between humans or from animals. You get West
Nile virus from mosquitoes.
I like to do outdoor activities. Am I at greater
risk for West Nile virus?
Outdoor activities are an important part of a healthy
lifestyle. Just because West Nile virus is in Utah
does not mean that people should stay indoors! You
can continue to enjoy the outdoors and easily protect
yourself by using mosquito repellent with DEET.
How can I tell if I was bitten
by a mosquito carrying West Nile virus?
Mosquitoes carrying West Nile virus do not look
or act differently than any other mosquito. The
bite from a mosquito carrying West Nile virus does
not look different than any other mosquito bite.
You can’t tell when you are bitten by a mosquito
that is carrying West Nile virus.
I have some really large mosquitoes
at my house, do they carry West Nile virus?
There are some insects that look just like mosquitoes
but are a lot larger. They are not mosquitoes and
do not carry West Nile virus.
What are some common West
Nile virus myths?
Visit this website: www.cdc.gov/ncidod/dvbid/westnile/Westnilespotlight2003.htm
Dogs, and Cats
(back to top)
Can West Nile virus cause
illness in horses?
Yes. The West Nile virus can cause serious illness
or death in horses. It is important to fully vaccinate
all horses against West Nile virus. Vaccine will
help protect horses against West Nile virus. For
further information, talk to your veterinarian or
check out information from the Utah Department of
Agriculture and Food at http://www.ag.state.ut.us/wnv/WNV&HorseOwners.pdf
Can West Nile virus cause
illness in dogs or cats?
Dogs and cats can become infected, but they rarely
show any symptoms or unusual behavior.
Is there a vaccine for cats
Can my I get West Nile virus
from my horse, dog, or cat?
There is no evidence that horses, dogs, or cats
will spread West Nile virus to humans.
Should a dog or cat infected with West Nile
virus be killed?
No. There is no reason to kill an animal just because
it has been infected with West Nile virus. Full
recovery from the infection is likely. Talk to your
veterinarian for more information.
Can I use insect repellent
on my pets?
DEET-based repellents, which are recommended for
humans, are not approved for use on pets (largely
because animals tend to lick their fur.) Talk with
your veterinarian for advice about the right product
to use on your pet.
Prevention and DEET Info (back
Protect from Dusk to Dawn
That is when mosquitoes that carry the virus are
most active, so protect yourself and your family
and prevent mosquito bites.
Protect yourself from mosquitoes
Use mosquito repellents that contain DEET* when
outdoors from dusk to dawn. (Follow the label instructions
carefully.) For adults, use repellents containing
up to 35% DEET. (Concentrations higher than 50%
do not provide additional protection.) For children
2 months–12 years, use repellents containing
up to 10% DEET. Do not put DEET on children’s
hands or feet. For children under the age of 2 months,
do not use DEET.
Use DEET when doing any outdoor
activity – even sitting on your porch
in the evening or taking a morning walk around the
* DEET is short for N,N-diethyl-m-toluamide
For extra protection, wear long-sleeved shirts and
long pants while outdoors. Use mosquito netting
when sleeping outdoors or in an unscreened structure
and to protect small babies any time they are outdoors.
Reduce mosquitoes around your
Control mosquitoes – Get rid of all
· Turn over or remove containers in your
yard where water collects, such as old tires, potted
plant trays, buckets, toys, etc.
· Clean out birdbaths and wading pools at
least once a week.
· Remove standing water on tarps or flat
· Clean clogged rain gutters and downspouts.
· Clean and stock garden ponds with mosquito-eating
fish or mosquito dunks.
· Recycle old bottles, buckets, and cans.
· Repair leaky faucets and sprinklers.
· Keep swimming pools clean or drain them.
· Make sure screen doors and window screens
are in good condition.
· Keep weeds and tall grass cut short; adult
mosquitoes look for these shady places to rest during
the hot daylight hours.
· Keep window screens on campers, tents,
and boats "bug-tight".
· Keep campsites neat. Get rid of mosquito
breeding sites. (Electric "bug zappers"
do not help since they usually attract more mosquitoes
than they kill.)
If you can’t get rid of the
water (for example, ornamental ponds, stock tanks,
· Use “mosquito dunks”. These
are small round disks of Bacillus thurengensis that
prevent mosquito larvae from hatching. They are
available in many garden stores and supply catalogs.
· Use mosquito fish. These are fish known
as Gambusia affinis, and are available from mosquito
Why should I use a mosquito repellent that contains
DEET is the most effective insect repellent available.
The more DEET an insect repellent contains, the
longer it will protect you. A higher percentage
of DEET does not mean it will protect you better,
just that it will last longer. For example, a product
containing approximately 10% DEET will last about
2 hours, and 24% DEET will last about 5 hours. However,
DEET concentrations higher than 50% do not increase
the length of protection.
Is DEET safe?
Yes, products containing DEET are safe when used
according to the directions. Always follow these
· Use enough repellent to cover exposed skin
or clothing. Don't apply repellent to skin that
is under clothing. Heavy application is not necessary
· Do not apply repellent to cuts, wounds,
or irritated skin.
· After returning indoors, wash treated skin
with soap and water.
· Do not spray aerosol or pump products in
· Do not apply aerosol or pump products directly
to your face.
· Spray your hands and then rub them carefully
over the face, avoiding eyes and mouth.
for more scientific information.
Should pregnant or nursing
women use DEET?
Women who are pregnant or nursing can use DEET.
Be sure to follow the directions carefully.
Is there a vaccine for West
There is no vaccine for West Nile virus at this
time for humans, however there is a vaccine for
Bird Information (back
What should you do if you
find a dead or ill bird?
A. What kind of bird is it?
Only some kinds of birds are appropriate for testing.
These birds are ravens, crows, jays, owls, hawks,
falcons, and eagles. You can also check out this
link for help in identifying birds: http://www.wildlife.utah.gov/wnv/bird_id.html.
If you see a dead bird that is not one of the above
types, carefully throw the bird in the trash*.
B. Did lots of birds die at
West Nile doesn’t kill many birds at the same
time. If you see many dead birds in your backyard,
they were probably poisoned. You can call the Division
of Wildlife Resources for further information http://www.wildlife.utah.gov/wnv/contact.html
C. How long has the bird been dead?
We can only test freshly-dead birds for WNV. Make
sure that the feathers are shiny, and that there
are no maggots or other signs of rot. If the bird
isn’t freshly-dead, then carefully throw the
bird in the trash*.
D. How do you report the dead
The easiest way is through on-line reporting at
Otherwise, call your:
Your local mosquito abatement district,
Local Division of Wildlife Resources ,
Local health department,
or UDOH Office of Epidemiology (801.538.6191).
E. What happens after I report
the dead bird?
Collect the dead bird*, but do not place it in the
garbage can. Instead, place it in a cool, shady
area. If possible, someone will come within 24 hours
and test the bird for West Nile virus. If no one
comes within 24 hours, discard the bird in an OUTSIDE
*How do I dispose of the dead
· Avoid touching the dead bird with your
· Use rubber gloves or put a double plastic
bag over your hand.
· Invert the bag over your hand, grab the
bird, wrap it up, and tie off or seal the bag.
· Throw the double bag and dead bird into
an OUTSIDE garbage container
· Wash your hands thoroughly with soap and
· You cannot get West Nile virus from the
Bird Feeder Cleaning Instructions
For routine cleaning: Clean feeders once a week
using a bleach solution - use one part bleach to
nine parts water. Rinse feeder thoroughly with water
after cleaning and allow it to dry completely before
refilling it with fresh seed. Remove waste grains
from below feeders.
If you have had birds die
near your feeder:
Use a stronger bleach solution to clean your feeder
- one part bleach to three parts water. Rinse feeder
thoroughly with water after cleaning and allow it
to dry completely before refilling it with fresh
seed. Also, remove waste grains from below feeders
and empty water for 7-10 days after an incident
where birds have died near your feeder.
Symptoms and Treatment
What are the symptoms of West
· Most people will not even know they are
· About 20% of infected people develop flu-like
symptoms. This is called West Nile fever. These
people may have a fever, body aches, and possibly
· Of those that become infected, 1 in 150
will go on to have the more severe form of the disease.
They may have a stiff neck, and muscle weakness,
and they may become confused or disoriented. Such
people may have seizures, go into a coma, and, in
rare occasions, may die. People over the age of
50 are at highest risk of getting the severe infection.
How soon do symptoms appear?
Symptoms can appear between 3 and 15 days after
a mosquito bite from an infected mosquito.
How long do symptoms last?
Symptoms of West Nile fever will generally last
a few days, although even some healthy people report
being sick for several weeks. Symptoms of severe
disease (encephalitis or meningitis) may last several
weeks, and some symptoms may become permanent.
How do I know if I have West
Other illnesses can cause symptoms just like those
described above for West Nile virus. The only way
to know if you have West Nile virus is to see your
health care provider. Your health care provider
will need to run laboratory tests to find out if
you have West Nile virus or not. If you are concerned
about your health or about the health of someone
in your family, please contact your health care
What is the treatment for
West Nile virus?
There is no specific treatment for disease caused
by West Nile virus. Antibiotics do not work. There
is no vaccine for humans. You must try and prevent
If bitten by a mosquito, should
I be tested for West Nile virus?
No. People rarely become sick from a mosquito bite.
However, people with a high fever, severe headache,
and muscle weakness or confusion should see a doctor
immediately. People with flu-like symptoms are likely
to recover completely and do not need to visit a
doctor. Even in areas where mosquitoes carry the
virus, very few mosquitoes are infected. The chance
that one mosquito bite will be from an infected
mosquito is very small.
If I have West Nile fever,
can it turn into West Nile Encephalitis?
Usually no. West Nile fever generally goes away
after several days. Some people may develop a brief,
West Nile fever-like illness (early symptoms) before
they develop more severe disease, although it is
not known how often this occurs.
Spread to Humans (back
How do people get infected
with West Nile virus?
The main way that humans become infected with West
Nile virus is through the bite of an infected mosquito.
Mosquitoes become infected when they feed on infected
birds. Humans do not become infected through direct
contact with other humans, horses, birds, or other
Can West Nile virus be spread
through blood transfusions?
Yes, but it occurs rarely. Blood banks are now screening
blood to make sure that it does not contain the
I am pregnant. If I get West
Nile virus, is my baby at risk?
In the United States, one case where a mother gave
her baby West Nile virus was documented during 2002.
Experts don’t yet know how much risk there
is to an unborn baby. Pregnant women should try
to avoid infection by wearing protective clothing
and using repellents containing DEET. Pregnant women
who become sick with a high fever and stiff neck
should see their doctor as soon as possible.
Are hunters who field dress
wild game birds at risk for West Nile virus?
There is no evidence that West Nile virus can be
spread directly from birds or mammals to humans
through direct blood contact. However, hunters are
always urged to take proper precautions and wear
rubber gloves when field dressing game.
Can a person get West Nile
virus by eating infected game birds?
Proper cooking kills the virus. There is most likely
no danger associated with eating well-cooked wild
game that might be infected.
Department of Health
Office of Epidemiology
June 15, 2004