Home / Infections / What is the West Nile Virus

What is the West Nile Virus

The West Nile virus was first isolated in 1937 in Uganda. It has always had a widespread area of distribution including Africa, the Middle East, Asia, and parts of Europe. It had never been isolated in the United States before 1999, when it was discovered to be the cause of 7 deaths and many cases of lesser illness in the New York metropolitan area.

The virus is carried by birds who are symptomatic and ultimately succumb to the illness. In the United States, mosquitoes are known to transfer the virus between infected and non-infected birds, and to humans. In other parts of the world, mosquitoes as well as bird mites and ticks are responsible for the spread of the virus, and for the capacity of the virus to survive the winter months. It is not known whether this mechanism of spread and “wintering” of the virus occurs in the United States as well.

Illness caused by the West Nile virus is called “West Nile Fever”. Often the virus will cause little or no illness in infected humans. In those who do have symptoms, fever, headache, sore throat, rash, joint aches, and gastrointestinal symptoms are most common. These symptoms resolve over 5 days. More seriously, however, the liver, heart, and most importantly, the brain can be involved. While nerve involvement and non-bacterial meningitis can occur, encephalitis is the most feared possibility. Encephalitis is inflammation of the brain with consequent brain injury, malfunction, swelling, and risk of seizures. Roughly 10% of West Nile Virus encephalitis cases are fatal.

Prevention

While experimental vaccines are being developed, currently the best way to prevent West Nile Fever is by avoidance. State and city programs are underway to reduce the mosquito population, and to survey the bird and mosquito populations for the West Nile virus. However, parents should additionally employ personal protective measures on themselves and their children.

Personal protection:

  • Mosquito repellant (DEET max 30% on the skin of children (not to be used under the age of 2 months), higher percentages for clothing). Of less proven efficacy is soy oil and other fragrant oils (e.g. citronella oil, Avon’s Skin So Soft). Wash all repellants off the skin once returning indoors for the night (i.e. a nightly bath is smart in the summertime for several reasons–to wash off sun blocks and insect repellants and to perform a tick check).
  • Wear hats, long sleeved clothing, and long legged pants when mosquito exposure is likely.
  • Avoid outdoor activity at dusk and dawn when mosquitoes are most active.
  • Environmental controls such as incense, citronella candles, smoke, and ultrasonic devices may be helpful.
  • Eliminate areas of standing water on your property–these are breeding grounds for mosquitoes.

Treatment of West Nile Virus

Currently there is no specific antiviral medication against the West Nile virus. Experimentation is ongoing to see if the virus may respond to other antiviral agents already in existence. Supportive treatment (e.g. intravenous fluids for those who are unable to eat) is usually only required by those who are severely ill.