West Nile Virus
Questions and Answers
What is West Nile Virus?
West Nile Virus (WNV) is one of several viruses spread by mosquitoes. It is closely related to St. Louis encephalitis (SLE) virus. SLE virus is most prevalent in the Southeast and Midwest U.S. WNV is also found in
Africa, Europe, and Asia (primarily in countries
bordering the Mediterranean). Infection with this
virus does not always result in clinical disease.
Studies have shown that normally only a small
percentage of humans infected with the virus will
show symptoms of disease and even fewer will develop
any serious complications.
Should I be worried about West Nile Virus?
No. Studies have shown that normally
only a small percentage of humans infected with the
virus will show symptoms of disease and even fewer
will develop any serious complications. The
disease caused by West Nile Virus is very similar to
St. Louis Encephalitis (SLE), but is generally
milder. SLE has been in the US for several years.
Human infections with these mosquito-borne viruses
are very rare and people can further reduce the risk by taking measures to avoid mosquito bites.
Is there a treatment for West Nile Virus for humans?
There is no specific treatment, medication, or
cure for illnesses caused by West Nile Virus. However,
the symptoms and complications of the disease can be
treated. Most people who get the illness recover from
Is there a vaccine to protect humans from West Nile virus?
There is not a vaccine to protect humans against West Nile virus infection.
Should I keep my children indoors?
No. The risks of acquiring a mosquito-borne
disease are so low that staying indoors is
unnecessary. However, if you are in an area with a
lot of mosquitoes, you can take some precautions
while you are outside, such as wearing long sleeves
and long pants and applying an insect repellent
(containing DEET) according to label directions.
A mosquito bit my child. Should he be tested for West Nile Virus?
Even if you live in an area where mosquitoes
are known to carry West Nile Virus or
other viruses, very few mosquitoes will actually be
infected and capable of transmitting the viruses to
humans. Even if an infected mosquito bites you,
chances of becoming ill are very low. If an
illness does occur after a mosquito bite,
particularly with fever, confusion, muscle weakness,
or severe headaches, or if your eyes become unusually
sensitive to light, you should consult your
physician. Your health care provider will determine
what kind of treatment you require and whether or not
you should have any specific laboratory tests
Why isn't my neighborhood being sprayed for mosquitoes?
Health officials in your county will likely
compare the risks of West Nile Virus infection
and the benefits of applying mosquito-killing sprays
in your community before providing a
recommendation. The most effective means of
prevention is the abatement of mosquito breeding
areas and larvicidal applications, when
appropriate. Broad applications of
pesticides by aerial spraying are not encouraged because it´s neither the most beneficial (because of it´s short duration) nor the most cost-effective way to control mosquito populations or mosquito-borne diseases. It can also harm beneficial insects. There are also concerns about people with chemical sensitivities and lung problems.
I have seen dead birds. Should I report them?
If you find dead birds, contact your county
health department and ask them if they need them for
WNV testing. Health officials are testing
crows, blue jays, and raptors (hawks) to determine
where the virus may
have spread. They may ask you to bring them in or
they may have all the samples from your area they
need for that week. Remember that birds may die
for many reasons. Some birds die of old age, some are
hit by cars or run into power lines, and some die of
Will the dead birds in my area make me sick from WNV?
No. The viral infection is spread from live
birds to people by the bite of a mosquito.
I sometimes set my pet canary
outside while I am working in my garden. Is it
Yes. It may be best
to keep birds indoors during peak mosquito feeding
times (dusk) and to check the integrity of window
screens. If you want your pet bird to have some
fresh air, keep it in a screened-in area or consider
mosquito netting over its enclosure.
What about chickens?
wild birds have been killed by WNV, it is unlikely
the disease would seriously impact the poultry
industry. The disease has not proven to be a
significant disease in poultry, and since most of the
U.S. chickens are housed inside, the risk is even
Can West Nile Virus cause illness in my cat or dog?
This is very, very unlikely. There are
no confirmed clinical cases of WNV in dogs.
Although two cats from New Jersey were reported with
the disease (one in 1999 and one in 2000), more
research is needed to determine if WNV is of
significant risk to cats. With the virus first
appearing two years ago in New York City and nearby
areas with high dog and cat populations, there likely
would be more clinical evidence of disease if dogs
and cats were susceptible.
Should I use insect repellent on my dog?
There are insect repellents available for
pets. Be sure to follow the label
directions. Products intended for humans can be
toxic to pets, however. Therefore, human repellants
should not be used on animals without a
Can West Nile Virus affect horses?
Yes. Horses can become sick and recover
or possibly die from WNV. It is likely that
many horses become infected with the virus but
recover without showing any clinical signs of the
Is there a vaccine to protect horses from WNV?
The U.S. Department of Agriculture has
approved a conditional license for a vaccine for
horses against WNV. It is uncertain how
effective this new vaccine is. Even if your
horses are vaccinated with the new vaccine, we advise
horse owners to keep all their other vaccinations up to date and practice mosquito control around their barns and stables.
(See our press release about mosquito control for
Where can I get this vaccine?
The vaccine will be available through your veterinarian.
Will vaccinating my horse
against Eastern or Western Equine Encephalitis
protect against West Nile Virus?
The equine encephalitis viruses and WNV belong to
different families, so the vaccines are not expected
to provide cross-protection.
Will other states quarantine against my horse if it is infected?
Infected horses do not appear to be carriers
of WNV so a quarantine is not helpful in controlling
Will boarding an
infected horse next to uninfected horses cause them
to get the disease as well? Can a mosquito bite
an infected horse and spread the disease to other
horses or to humans?
uninfected horse with an infected one will not lead
to the other one becoming infected. A mosquito
that is not already carrying West Nile Virus cannot
pick up the virus by biting a horse or a human.
The virus is not concentrated enough in the blood of
humans or horses to be spread this way.
Will West Nile Virus affect my cattle?
Will an electric ``bug zapper" help control mosquitoes
in my yard or barn?
No. These are a waste of
money. In fact, bug zappers actually make
things worse by attracting more mosquitoes to the
area, and they end up killing thousands of beneficial
insects that do not bother people. Another
drawback is the electric grid that kills the insects
can cause the trapped insect to explode, spraying
harmful bacteria into the surrounding area. Not
a pleasant thought as you bite into that hamburger
you grilled near your bug zapper.
What about machines that emit ultrasound to keep mosquitoes away?
They are a waste of money.
I saw an advertisement for a
type of scented geranium that would help repel
mosquitoes. Will this work?
oils in some scented geraniums may have some mild
mosquito-repellent properties if you rub them on your
skin. The ads are totally false that claim if
you grow these ``mosquito plants" they will
repel mosquitoes. Planting a whole garden of
them would not deter even one mosquito.
Are citronella candles and coils effective at repelling mosquitoes?
Their effectiveness is limited to small areas
(a few feet) and windless conditions.
I would like to put up
a bat house for bats to roost in. I hear they
eat lots of mosquitoes. Do you have any
Bats can eat a lot of mosquitoes and other insects as well. There are estimates that some species can capture 500 to 1,000 mosquitoes per hour. In many areas bat populations have been decimated by loss of habitat and ignorant destruction. Installing a bat house is a way to help these misunderstood and maligned creatures make a comeback. But will installing a bat house solve your mosquito problems? It’s a first step in the right direction. First of all, there have to be bats in
your area looking for a place to roost and your bat
house must meet all the requirements as to design and
location for the bats to take up long-term residence
there. If bats
move into your bat house, do not expect them to stay
within your property during their nightly forays and
feed only on mosquitoes that are trying to feed on
I hear purple martins eat a lot of mosquitoes. Is this true?
Attracting a colony of purple martins with
gourds or a purple martin house is a good way to
enjoy the song and aerial acrobatics of these
beautiful birds. They eat many flying insects
but not the large numbers of mosquitoes so often
claimed by companies that manufacture purple martin
housing. For more information about these
birds, contact the Purple Martin Conservation
Association, Edinboro University of Pennsylvania,
Edinboro, PA, 16444 (Telephone: 814-734-4420)