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West Nile Virus - Frequently Asked Questions


How Can West Nile Virus Be Transmitted?

West Nile Virus is carried in birds and transmitted to other birds mostly by mosquitoes.  The virus spreads through mosquito bites and can infect mammals including humans.  Some research has indicated that WNV can be transmitted from bird to bird without a mosquito vector, however this mechanism of transmission is unknown. 


For transmission to humans, in 2002 the Center for Disease Control confirmed additional routes of transmission which include**:

    • infection through transplanted organs
    • one case of transplacental (mother-to-child) infection
    • one case of transmission through breast milk
    • blood transfusion-associated transmission

**These routes of transmission represent only a very small proportion of WNV cases.

NOTE: West Nile Virus cannot be transmitted through touching.



Is a Dead Crow a Sign that there is West Nile Virus in the Area?

Yes, a dead crow potentially signals the presence of the virus.  Additional, blue jays and ravens are also susceptible to West Nile Virus and may indicate its presence in an area.  The Michigan Department of Natural Resources (DNR) recommends that you report the sighting of ANY dead birds or mammals.  It will then be decided by the DNR whether the dead animal should be submitted for WNV testing.  Please refer to the State of Michigan website for more information on reporting a dead animal.


What Can I Do to Prevent West Nile Virus?

The Center for Disease Control (CDC) states the primary precaution against WNV should be to avoid mosquito bites.  The CDC recommends:

  • When outdoors, use an insect repellent that contains EPA-registered active ingredients:  DEET, Picaridin, or repellents containing oil of lemon eucalyptus.
  • If possible, stay indoors during dusk and dawn – the times of the day that mosquitoes are most active.  If outside during these hours, protect yourself with repellant and long-sleeved shirts and pants.
  • Maintain secure screens and doors to your home.
  • Minimize mosquito breeding areas by emptying standing water in flower pots, buckets and barrels.  Make sure to changes water in pet dishes and replace bird bath water weekly.  Drill holes in tire swings so that water drains out and keep children’s wading pools and slides empty when not in used.

What Are The Symptoms of West Nile Virus?

NO symptoms in most people: Approximately 80% of people (4 in 5) infected with WNV do not show any signs of infection.

Mild Symptoms

Fever, headaches, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back.  These symptoms could last a few days to a few weeks, even in healthy people.  ONLY ABOUT 20% OF THE PEOPLE WHO BECOME INFECTED WILL SHOW SIGNS OF MILD SYMPTOMS.


Serious Symptoms

High fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.  Such symptoms could last for a few weeks, and neurological effects could be permanent.   ONLY ABOUT ONE IN 150 PEOPLE INFECTED WITH WNV WILL DEVELOP A SERIOUS ILLNESS.    


If I Get Infected By West Nile Virus, How Long Would It Take For Me To Become Ill?

The majority of  people infected with West Nile will not show any signs of symptoms.  However, it you do become ill from becoming infected with the WNV, it may take between 3 and 14 days to develop symptoms.



What Should I Do If I Think I Have West Nile Virus?

Those that show serious symptoms of infection usually need to be hospitalized and receive treatments such as intravenous fluids, breathing aid, and nursing care.  People who do not show serious signs of illness may not even require treatment as the symptoms naturally subside.  There is no specific treatment for the WNV. 


Can My Pets Contract the West Nile Virus?

Dogs and Cats

WNV has appeared in dogs and cats, but at very low infection rates. You should take your pet in to see your veterinarian as usual, and most likely the veterinarian will treat the symptoms like any other viral infection. Full recovery is likely. There are no documented cases of the virus being transmitted from pet to humans, as the infection is transmitted by mosquitoes.



Horses, like dogs and cats, can be infected with WNV. Veterinarian attention should be sought after for infected horses. There are no documented cases for which WNV has been transmitted from one horse to another in a neighboring stall, but infected horses should be isolated. There is a WNV vaccination for horses; if you are interested, talk to your veterinarian.


Who Do I Call If I Find a Dead Bird?

The Michigan Department of Natural Resources (DNR) recommends that you report the sighting of ANY dead birds or mammals.  It will then be up to the DNR whether the dead animal should be submitted for WNV testing.  Please refer to the State of Michigan link for more information and instruction on how to report a dead animal.

(2009 Update: To report dead birds please contact the Oakland County Health Department at (877) 377-3641.)



For more information call the Center for Disease Control public response hotline at   (888) - 246 – 2675 or the Oakland County Health Department at

(877) – 377 - 3641.   


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