West Nile Virus (WNV) is a mosquito-borne virus that was first detected
in the United States in 1999 and in Arizona in 2003. It is not known how
the WNV was introduced into the United States but it may have entered in
an infected traveler, bird, or mosquito. WNV has been present in Africa,
West and Central Asia, and the Middle East for a long time. The virus
can cause illness in people, horses, certain types of birds, and other
animals. The majority of people and animals that are infected with WNV
have no symptoms or only a mild illness. Approximately 20 percent of
infected people will have "flu-like" symptoms such as fever, headache,
body aches, swollen glands and muscle weakness. Symptoms can last
for days or weeks. In rare cases, WNV can cause more serious conditions
such as encephalitis (an inflammation of the brain) and/or meningitis
(an inflammation of the linings of the brain and spinal cord).
How do mosquitoes become infected with West Nile Virus?
Mosquitoes become infected with WNV when they feed on birds that are
infected with WNV. After a few days, infected mosquitoes can then
transmit WNV to other birds, humans and horses. Only certain species of
mosquitoes carry the virus.
Culex mosquitoes are the main carriers of WNV, and these
mosquitoes are common throughout Arizona. Culex
mosquitoes tend to bite from dusk to dawn.
How do people become infected with West Nile Virus?
People become infected with WNV from the bite of an infected
mosquito. Birds and other animals cannot transmit WNV to people.
In 2002, a small number of people in the United States became infected
with WNV when receiving blood products or organs from WNV infected
donors. In 2003, a blood testing program was initiated to screen blood
products for WNV prior to transfusion.
What is "encephalitis"?
Encephalitis is an inflammation of the brain. In some cases, WNV can
cause encephalitis.
Signs and symptoms might include high fever, headache, confusion,
disorientation, seizures, muscle weakness, and coma.
Who is at risk of getting sick from West Nile Virus?
People of all ages can get sick from West Nile virus infection, although
the chance of becoming seriously ill is low. Persons over the age of 50
are generally at a higher risk for serious illness. West Nile
virus activity can occur anywhere in the State. Everyone should
take steps to "Fight-the-Bite."
What are the symptoms of West Nile Virus infection?
Most people who are infected with WNV have no symptoms or may experience
a flu-like illness, such as a fever, headache, weakness and swollen
glands. For some people, illness can last for weeks. In some
individuals, particularly in those over age 50, WNV can cause more
severe illness such as meningitis and/or encephalitis. Symptoms
generally occur three to 15 days following the bite of an infected
mosquito. Symptoms may include high fever, headache, stiff neck,
muscle weakness or paralysis, seizures, confusion and/or disorientation.
Of the most serious encephalitis cases, approximately 3-15% may be
fatal.
Is there a treatment for West Nile Virus infection?
There is no specific treatment for WNV infection. As with other viral
illnesses, supportive care and symptomatic therapy are given.
Is there a vaccine to prevent West Nile Virus infection?
There is no vaccine currently available to protect people against West
Nile virus infection. However, research is underway to develop a vaccine
for people. There is a vaccine available for horses. Contact your
local veterinarian for more information.
Can I get WNV from another person or an animal?
No. WNV is not spread by person-to-person contact or directly from
animals to people.
If bitten by a mosquito, should I be tested for WNV?
No. You do not need to be tested unless you develop West Nile
virus symptoms.
What time of year are mosquito-borne viruses spread?
In Arizona, mosquito-borne viruses are most likely to be spread from
April through October during the peak of mosquito activity.
How can I help protect myself and my family from West Nile Virus?
The best way to protect you and your family from WNV, or any other
mosquito-borne illness, is to reduce the number of mosquitoes around
your home and neighborhood and to take personal precautions to avoid
mosquito bites. These are some of the preventative steps that you can
easily take:
-
Eliminate standing water where mosquitoes can breed. Check for items
outside the home that collect rain or sprinkler water, such as cans,
bottles, jars, buckets, old tires, drums, wheelbarrows, boats, kid
pools, and other containers.
-
Change water in flower vases, birdbaths, planters and animal
watering pans at least twice a week.
-
Repair leaky pipes and outside faucets, and move air conditioner
drain hoses frequently.
-
Avoid being bitten by mosquitoes when going outside at night by
using
insect repellent. Wear lightweight clothing that covers the
arms and legs.
- Report mosquito breeding problems (e.g. green pools) to your local environmental health office.
Which animals can get infected with West Nile Virus?
WNV infection has been reported in more than 280 bird species.
Certain types of birds such as crows, ravens and jays appear to be most
susceptible to WNV infection. Horses
are also susceptible to WNV infection but a vaccine is available
through veterinarians. WNV infections affecting the nervous system have also
been reported in squirrels, goats, sheep and llamas, but the susceptibility
of these animals to WNV is not well known. WNV illness in dogs and
cats is rare. Contact your veterinarian for information about pets and
livestock.
What should I do if I find a dead bird?
If you find a dead bird, you should contact your
county
environmental health department for more information. A
program has been established to test dead birds reported in Arizona.
However, not all dead birds can be tested for WNV. To be tested, the dead
bird should be relatively fresh, not scavenged or decomposed, and with
little or no odor. Also, testing is not being offered for baby birds
or pigeons. Always wear gloves when handling dead birds. Refrigerate
the dead bird until it is
submitted for testing [PDF
16K]
(but Do Not Freeze it!).
Can a person get West Nile Virus infection by eating infected birds?
Proper cooking kills WNV. Consequently, there is no danger associated
with eating birds that have been properly cooked. Hunters are
encouraged to wear gloves whenever field dressing game, including birds.
What is Arizona doing to prepare for West Nile Virus?
County and state health workers monitor and test mosquitoes at selected
sites, dead birds and sentinel chicken flocks (17) for mosquito-borne
viruses. Mosquito surveillance involves trapping mosquitoes, counting them,
identifying the species involved, and testing the appropriate species for
viruses. These surveillance methods are used to better identify areas where
mosquito control efforts are needed. Detection and control of mosquito
breeding sites depends upon integrated efforts among state, county, and
tribal agencies as well as private citizens.
Where can I get more information on West Nile Virus?
Call your local health department for additional information. Or call
Arizona's 24-hour
bi-lingual Public Health Hotline for the latest information about WNV at
(602) 364-4500 in Metro Phoenix or 1-800-314-9243 in other areas of the
state. You can also contact the Arizona Department of Health Services
Vector Borne & Zoonotic Disease program at (602) 364-4562.
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