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West Nile Virus (WNV)

Books on West Nile Virus  from Amazon.com

21st Century Collection Centers for Disease Control (CDC) Emerging Infectious Diseases (EID)

 

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CDC, 2002

West Nile Virus

 

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by Despommier (2001) 

West Nile Virus: Detection, Surveillance, and Control (Annals of the New York Academy of Sciences, V. 951)

 

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by White & Morse (Eds.) (2001)

West Nile Virus: Overview and Abstracts

 

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by Lee (ed.) (2003)

West Nile Virus (Epidemics)

 

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by Margulies (2003)

 

Epidemic/Epizootic West Nile Virus in the U.S: Revised Guidelines for Surveillance, Prevention, and Control

 

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by Gubler (Ed.) (2001)

Article - West Nile Virus Update

 

Extracted from the "Clinical Nursing Resources" Newsletter, Volume 1, Number 16

 

The West Nile virus (WNV) was first documented in Uganda in 1937. For years, WNV was only found in the Eastern hemisphere, especially in Africa. WNV was first identified in the United States in New York City in 1999. Additional cases are identified and deaths are reported daily. 

 

Mosquitoes transmit WNV when they bite humans. They also pass the virus to birds (especially crows), horses, and smaller animals.  The virus is particularly virulent in birds. Humans do not contract WNV by handling birds who have succumbed to it. They must be  bitten by an infected mosquito. The more bites, the more exposure.

 

Horses and small animals have relatively low levels of the virus and do not transmit the disease. The incubation period of WNV is from three to 14 days.

 

SYMPTOMS

 

The WNV travels through the blood-brain barrier and can cause viral encephalitis, meningitis, or both. Most victims experience no symptoms or mild flu-like symptoms: Fever, headache, anorexia,  nausea and vomiting, myalagia, eye pain, rash, and enlarged lymph glands. 

 

WNV affects all races and men and women equally. The illness lasts three to six days. The elderly, chronically  ill, or immunosuppressed are more likely to become seriously ill or die from WNV. 

 

Symptoms of viral encephalitis include confusion and a decreased  level of consciousness. Symptoms of viral meningitis include a stiff neck, a positive Kernig sign, or a positive Brudzinski sign.  Both the Kernig sign and the Brudzinski sign are tests of meningitis. 

 

To perform the Kernig sign, flex the person's thigh and extend the leg at the knee.  If the patient resists or complains of  pain, the sign is positive.

 

To perform the Brudzinski sign, flex one of the person's legs. The sign is positive if the other leg flexes on its own.  In another version, bending the person's head down results in flexion of one or both of the hips, knees, or ankles.

 

LABORATORY TESTS

 

The following tests are used to diagnose WNV:

  • igM antibody-capture ELISA test - to detect antibodies to WVN in the serum or cerebrospinal fluid. The WNV antibody remains in the body for about six months.

  • Identification of the West Nile virus in the blood.

  • Lymphocytopenia, anemia, and an elevated cerebrospinal fluid protein. Note that false positives are possible in these tests since the virus is related to similar diseases, such as St. Louis encephalitis.

A case is considered to be "probable WNV" when the WNV antibody is identified and "confirmed WNV" when the virus itself is identified.

 

TREATMENT

 

The treatment is entirely supportive. Patients with mild cases are urged to drink fluids, get plenty of rest, and take antipyretics. Those who end up with encephalitis or meningitis often require intensive care, antiseizure medications, mechanical ventilation, and fluids and electrolytes.

 

PREVENTION

 

Urge the  public to 

  • Drain any collections of stagnant water found in the environment.

  • Use mosquito repellants when they are outside. The strength should be no more than 10% (DEET) for children and 10-50% for adults. Treat clothing, skin, bedding, tents and tent screens. Avoid getting mosquito repellant on the hands to prevent getting any into the mouth, eyes, ears.

  • Wear long sleeves and long pants. 

  • Avoid wearing bright colors or using perfumes. Both may attract mosquitoes.

  • Stay indoors from dusk to dawn, when mosquitoes are more active.

  • Report dead birds to state and local health departments.

Governments are spraying two types of chemicals on mosquito-

infested areas:

  • Natural larvocides, such as is Bacillus thuringiensis var. israelensis or Bacillus sphericus.

  • Methoprine to kill adult mosquitoes, which can cause eye irritations or skin rash, though the incidence is rare.  

BIBLIOGRAPHY

 

Centers for Disease Control (2002). Prevention: Avoid mosquito bites to avoid infection. Retrieved August 12, 2002. http://www.cdc.gov/ncidod/dvbid/westnile/index.htm.

 

Cunha, B.A. (2002). West Nile encephalitis. Retrieved September 15, 2002. http://www.emedicine.com/med/topic3160.htm. (Requires free registration to access).

 

Petersen, L.R., & Marfin, A.A. (2002). West Nile virus: A primer for the clinician. Annals of Internal Medicine(137), 173-179.

 

Summary by Becky Sisk, PhD, RN (c) December, 2002

 

Students: Consider this a secondary source for information about WNV.  Go to the primary sources on this page to find references for your paper or preparation.