West Nile Virus

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What YOU Need to Know!

Idaho Department of Health & Welfare West Nile Virus - Fight the Bite! Informational Website

Who to call for West Nile Virus information (pdf)

What is West Nile Virus?

• West Nile Virus (WNV) is a virus transmitted by mosquitoes commonly found in Africa, West Asia, and the Middle East.
• WNV was first identified in Uganda in 1937.
• First documented in the U.S. in 1999.
• Following transmission by an infected mosquito, WNV can multiply in a person’s blood system and sometimes crosses the blood-brain barrier.
• If WNV interferes with normal Central Nervous System functioning, it can lead to encephalitis (inflammation of the brain) or meningitis (inflammation of the meninges).

Consequences

• It is estimated that 20% of people infected with WNV will develop West Nile Fever.
• Less than 1% (about 1 out of  150) of those infected with West Nile Fever develop severe disease such as encephalitis or meningitis.
• There is no documented evidence that a pregnancy is at risk due to a mother’s infection with WNV.

What Are Symptoms of West Nile?

Many people infected with West Nile Virus will not develop symptoms.  However, for those who do, it will most likely be a mild infection characterized by:

• Fever, Headache, Body aches, Skin rash, Swollen lymph nodes

There are no known long-term effects due to mild illness.

Very few people will develop a severe infection known as West Nile meningitis and/or encephalitis (inflammation of the brain and/or meninges.  It may be accompanied by the following symptoms:

• Headache, High Fever, Neck Stiffness, Stupor, Disorientation, Coma, Tremors, Convulsions, Paralysis, Death

What Is The Incubation Period?

• West Nile Virus usually takes 3-14 days for symptoms to develop.
• Symptoms, if the disease is mild, will generally last from 3-6 days.
• Symptoms of severe illness can last up to several weeks and neurological effects can be permanent.

Prevention Measures

• Stay indoors at dawn, dusk, & early evening hours when mosquitoes are most common.
• Wear long-sleeved shirts and long pants whenever you are outdoors.
• Spray clothing with repellents containing DEET.
• Eliminate potential mosquito breeding grounds (such as standing stagnant water, old tires full of water, bird baths, feeding troughs, etc.).
• Fix window and door screens.

Horses

• WNV can cause severe illness & death in horses.
• Horses are infected through a mosquito bite.
• An equine WNV vaccine is newly available but takes 7-12 weeks before maximum resistance to WNV.
• Symptoms include: stumbling, incoordination, weak limbs, partial paralysis, muscle twitching, and in some instances a fever.
• Horses have a 30-40% mortality rate if they contract WNV.
• Contact your local veterinarian for vaccine information.

 Pets

• WNV does not appear to cause any serious illness in dogs or cats.
• If dogs or cats have WNV, full recovery is likely.
• Treatment would be consistent with standard veterinary care for viral agents.
• Some birds may be at risk.
• Contact your veterinarian to find if your pets are at risk and what prevention measures to take.

Informational Links:

• Center for Disease Control
  West Nile Virus Information Page
• Idaho Department of Health and Welfare
  West Nile Virus Information Page
• Idaho Fish and Game
• American Academy of Pediatrics
  "Follow Safety Precautions when using DEET on Children"
• National Pesticide Information Center
• US Environmental Protection Agency
• Where is West Nile at Today?
  Center for Disease Control Map

For more information, contact:

Jeff Doerr, Epidemiologist

(208) 478-6321

Kathy Reynolds, RN, MPH, Epidemiologist

(208) 239-5231