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West Nile Virus (WNV) is now present in Western Washington. This viral illness is
foremost a disease of birds and secondarily mammals, but humans can become accidental hosts and, if infected, a few
may suffer serious to fatal consequences. Despite the media excitement about this disease, it must be remembered
that humans are fairly resistant to this virus, and infected humans rarely become sick enough to show any symptoms.
To date, about 1 person in every 150 infected has developed severe symptoms of infection.
WNV is mainly transmitted by mosquitoes, and does not spread from person to person. However, it may be transmitted by
accidental wound contamination from body fluids from infected birds, and less likely, mammals. Therefore, the most
effective control plan will strike at the weakest link in the chain of transmission, the insect vector.
Nine mosquito species resident in King county are currently known to transmit WNV; most likely there will be others.
All species require water to be present long enough for eggs to develop into larvae that ultimately mature into
adults. Maturation is dependent upon temperature, but usually takes from one to 3 weeks in Western Washington.
Spraying for adults is the least effective method to reduce mosquito populations compared to egg and larvae control.
Protecting against WNV for most people consists of preventing mosquito bites. This can be done in two ways:
- Protecting oneself from biting mosquitoes
- Reducing the number of mosquitoes breeding sites at home and standing water
- Recycle or invert containers
Protect yourself:
- Make sure windows and doors are "bug tight." Repair or replace damaged screens, and don't prop windows and doors open.
- Use insect repellent containing up to 35% DEET when going outside. Read and follow label instructions.
Take special care when using repellent on children.
- Avoid mosquito-infested places or wear a long sleeved shirt, long pants, hat, and repellent when going into
areas like woods or wetlands.
- Stay indoors around dawn and dusk when mosquitoes are most actively feeding.
Protect your neighborhood by eliminating standing water:
- Empty anything outdoors that holds water, e.g., tires, flower pots, planters, buckets, plastic or metal covers,
toys, and wading pools.
- Change water in birdbaths, fountains, wading pools, animal troughs, etc. at least once a week.
- Recycle containers that can hold water, like cans, bottles, and buckets.
- Make sure roof gutters drain properly. Clean clogged gutters in spring and autumn or whenever they need it.
- Fix leaky outdoor faucets and sprinklers.
- Discuss this issue with neighbors, and encourage them to remove breeding sources on their property.
Please help define how serious the WNV problem is in Western Washington by reporting dead crows, jays, ravens, and
magpies to the health department. Not all birds can be tested, and there will be a limited time in which testing will
occur.
To report a dead bird or animal and to find out if a bird needs to be collected for testing on the University
of Washington campuses, call EH&S at 206.543.7388.
If you have found a dead bird elsewhere, consult your local health department:
- King County - http://www.metrokc.gov/health/westnile/surveillance.htm
- Pierce County - http://www.co.pierce.wa.us/pc/services/home/property/pals/other/westnilevirus.htm
- Snohomish County - http://www.snohd.org/snoWNileVirus/index.htm
University of Washington's Urban Ecology Project is conducting a study on crows. If you find a crow with a colored band
on its leg, you have found one the crows in the study. When you call to report the dead crow you found, please mention
that it has a colored band on its leg. To learn more about the University of Washington's study,
visit www.urbanecology.washington.edu/Crows/westnile.htm
There is no evidence yet that humans can get WNV from touching dead birds, however, if you want to submit a bird for
analysis or dispose of a dead bird, follow these instructions:
- Consult your local health department (or EH&S if found on campus) to find out whether the bird needs to be
collected for testing as described above.
- Do not touch the bird with bare hands; use a plastic bag, gloves, a shovel, or some other barrier to prevent direct
contact.
- Put the bird in a plastic bag and clip or tie it closed; then put this inside another plastic bag.
- Follow the health department's instructions: tell the health department where the bird is. They will inform you
if the bird can be picked up or if it should be disposed of in a garbage can. Only fresh birds can be sent away for
analysis.
- Wash your hands afterward.
Field Research
WNV does not spread from person to person, and protecting oneself against mosquito bites is the first line of defense.
Field personnel should be sure their tents have netting to exclude mosquitoes, and should kill mosquitoes that get into
their tents. Outdoors, mosquito repellents with at least 35% DEET and clothing should be used to minimize bites.
Field researchers should be aware that, besides mosquitoes, almost any bird or mammal could be infected with WNV, which
may in turn expose the researcher to WNV. The researcher should keep in mind that the list of avian and mammalian
species now known to be susceptible to WNV infection is diverse, incomplete and growing. For an up-to-date list of
species known to be positive, consult the following web site:
http://www.nwhc.usgs.gov/disease_information/west_nile_virus/
WNV can be contracted from cuts and abrasions contaminated with bird and potentially other animals' bodily fluids.
Therefore, using personal protective equipment is recommended. Depending on the level of contact when working on or
with birds or other potentially infected animals, the following should be considered:
- latex or nitrile gloves (to prevent skin contact),
- protective outer garments (to protect clothing),
- steel mesh or cotton gloves (to prevent cuts), and
- protective eyewear (to prevent splash/squirts in eyes).
Additionally, a disinfectant, like a 10% bleach solution, is recommended for surface and equipment decontamination.
Avian Laboratory Animal Research
The same precautions apply to persons doing research and necropsies in laboratory settings with avian species. Similar
steps should be taken to avoid receiving cuts/abrasions/needle sticks from contaminated dissection and other instruments.
Laboratory workers doing necropsies or other procedures involving materials potentially infected with WNV should use
every precaution to minimize their exposure risk to fluids or tissues during handling, including: standard droplet and
contact precautions, using and disposing of needles, scalpels, and other sharp instruments safely, and minimizing aerosol
generation. Along with the above recommendations for field researchers, the CDC currently recommends that WNV infected
bird dissection be done inside a biological safety cabinet with appropriate personal protective equipment, even though
WNV has not been transmitted by aerosol. Guidelines are available from the Department of Comparative Medicine Veterinary
Services: 206-543-6257.
The two known instances of laboratory-acquired infections, one from a cut and the other from a needle puncture, are
described in the MMWR article cited on the web site below which recommends:
"Participating laboratory employees should receive training that reinforces awareness of potential occupational hazards
and risks and that stresses the importance of timely reporting of all injuries and illnesses of suspected occupational origin.
After unintentional laboratory incidents of potential exposure to WNV-infected materials, an exposed person should
cleanse any wound or exposed skin immediately and thoroughly, receive first aid, and then report the incident to a
supervisor, as was done in the two cases described in this report. No antivirals or other drugs are known to be
effective in the prevention or treatment of WNV infection. A baseline serum specimen should be obtained and stored. If
a worker has an illness within 2 weeks after an exposure, prompt medical evaluation, consultation with public health
authorities, and collection of additional serum samples for virologic and serologic analysis are recommended."
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5150a2.htm
Fact Sheet
This fact sheet (pdf) on the West Nile Virus is published by Seattle, King County Public Heatlth, Communicable Diseases and Epidemiology - Prevention Division.
Other Informative Sites
People wanting to find out more about WNV and precautionary measures which should be taken are encouraged to consult
the following web sites:
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