Klamath County Public Health-

Communicable Disease

West Nile Virus

West Nile Virus (WNV) is present across the United States, and in Oregon.  WNV is spread by mosquitoes and can result in serious, life altering outcomes and even death.  WNV mainly infects birds, but when a mosquito bites an infected bird the mosquito carries the virus and can then transmit the disease to humans. 

Although humans and some other animals may get sick when infected with West Nile virus, it is thought that they usually do not develop enough virus in the bloodstream to infect mosquitoes. For this reason, humans and animals such as horses are referred to as incidental hosts. West Nile virus is generally not spread from person to person.  However, in a very small number of cases, it has been transmitted through blood transfusions, organ transplants, breastfeeding, and even during pregnancy from mother to baby.  It is not transmitted by casual contact such as kissing or touching.

In Oregon positive tests for West Nile Virus have occurred. In August 2010, mosquitoes tested positive for West Nile Virus at a site near Irrigon in Morrow County. This is the first positive test in Oregon this year.

Most people with WNV may not have symptoms or have only a mild illness. However, the illness caused by West Nile virus may be serious and may include encephalitis, inflammation of the brain, or meningitis.  People may become ill 3 to 15 days after the bite of an infected mosquito.

Common signs and symptoms of West Nile virus infection include:

  • Mild illness with fever
  • Headache
  • Muscle aches
  • Backache
  • Skin rash
  • Swollen lymph glands

Encephalitis is an inflammation of the brain that may be marked by:

  • Severe Headache
  • High fever
  • Stiff neck
  • Stupor
  • Disorientation
  • Coma
  • Tremors
  • Convulsions
  • Muscle Weakness
  • Paralysis

See your doctor as soon as possible after you experience signs and symptoms that might suggest West Nile encephalitis. Although most people infected with the virus recover fully, the virus can result in serious, life-threatening illness.

Avoid Mosquito Bites:
-Apply an insect repellent that contains 20 percent to 30 percent DEET to exposed skin when you go outdoors. The more DEET a repellent contains, the longer time it gives protection from mosquito bites.  Other effective repellents include Picaradin, and EPA-registered oil of lemon eucalyptus preparations.
-Whenever possible, wear protective clothing such as long sleeves, long pants and socks when outdoors.
-Spray clothing with repellents containing DEET, because mosquitoes may bite through thin clothing.
-Consider staying indoors between dusk and dawn, which is peak mosquito biting time. Avoid activities in areas where mosquitoes are plentiful.
-Fix or install window and door screens to keep mosquitoes out of buildings.

Avoid Breeding Mosquitoes:
Mosquitoes lay their eggs in standing water. To avoid helping mosquitoes breed in your environment, drain standing water. Routinely empty water from flower pots, pet bowls, clogged rain gutters, swimming pool covers, discarded tires, buckets, barrels, cans and other items that collect water in which mosquitoes can lay eggs.

Video Clip on protecting yourself from West Nile Virus