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Introduction to West Nile Virus Awareness Training



West Nile Virus:

Virus Transmission Cycle



Reservoirs and Clinical Description



  • Birds are considered to be the main vertebrate host. Over 70 species of birds (mostly crows) tested positive
  • Clinical signs have been observed in horses
  • Cattle, Sheep, Camels can be infected, but viremia capable of infecting vectors has not been reported


Classical Clinical Description

Other Clinical Information


Most illnesses are manifested by "West Nile Fever"


Severe neurologic illness categories


Movement Disorders

Tremor:  a rhythmic, involuntary muscular contraction characterized by a to-and-from movements of a part of the body.

Myoclonus:  brief, involuntary twitching of a muscle or a group of muscles.

Both tremor and myoclonus—onset generally > 5 days following initial symptoms

Rhabdomyolysis—acute destruction of skeletal muscle cells




Spread of West Nile Virus in the
United States


Spread on WNV in the US

Cases of WNV In the US





West Nile Virus Program


WNV Program Elements


  • Dead bird
  • Mosquito


  • Chemical
  • Mechanical
  • Cultural





Dead Birds

Larvae breeding sites




Larval Control

Reduction of Mosquito Breeding Sites

Eliminate standing water and containers

  • Tires and tire swings
  • Flowerpots
  • Pet dishes
  • Bird baths
  • Clogged rain gutters

Mosquito Control

Personal Protective Measures

  • Long Sleeves
  • DEET
  • Limit outdoor activities at dawn, dusk, and early evening
  • Repair holes in door and window screens





Identification of Mosquito Adults


Mosquitoes Positive for WNV

  • Culex pipiens
  • Cules restuans
  • Culex salinaruius
  • Aedes vexans
  • Aedes cantanor
  • Ochlerotatus triseriatus
  • Ochlerotatus japonicus
  • Aedes albopictus
  • Anopheles punctipennis
  • Psorophora ferox
  • Culiseta melanura


Not all may be competent vectors!

Communication And Education



  • Most mosquitoes are not infected with West Nile Virus
  • Most mosquito bites will not lead to a West Nile Virus infection
  • Most people who become infected do not get sick
  • In US outbreaks, fewer than 1% of infected people became seriously ill
  • Children are not in a higher risk group
  • Older people and the immuno-compromised have greater risk of becoming seriously ill
  • There is no vaccine or medication specific to WNV—treat the symptoms


Medical should closely liaise with:

  • Local or State Health Departments
  • Base Pest Control
  • Local or State Mosquito Control Districts
  • U.S. Army Veterinary Services

Information resources

  • State and local Mosquito Abatement Districts
  • State and local Health 1-800-871-9703
  • CDC Website:
  • USGS Website: