West Nile virus

Nevada RNformation, Nov 2003

What is West Nile virus?

West Nile virus (WNV), is a mosquito-borne disease that can cause encephalitis, or a brain infection. Mosquitoes acquire the virus from birds and pass it on to other birds, animals and people.

Mosquitoes spread this virus after they feed on infected birds and then bite people, other birds and animals. It is not spread by person-to-person contact and there is no evidence that people can get the virus by handling infected animals.

Surveillance for WNV was initiated in Nevada in the Spring of 2001 and currently involves the reporting and testing of dead birds, mosquito pools, sentinel chicken flocks, and random blood sampling of any wild horse gather performed by BLM or Department of Agriculture.

Historically, Nevada has experienced two kinds of Encephalitis: Saint Louis Encephalitis (SLE), and Western Equine Encephalitis (WEE).

West Nile virus cases occur primarily in the late summer or early fall, although the mosquito season is April through October.

What is an Arboviral Encephalitis?

An Arboviral Encephalitis is an infectious disease that affects the brain. The disease is caused by a virus which attacks the brain, destroys some nerve cells and causes brain inflammation and swelling. Encephalitis arboviruses belong to several families of viruses that usually infect birds and are transmitted from bird to bird by mosquitoes. The name "ar-bo-virus" comes from the fact that they are transmitted by arthopods (insects and other "bugs").

What is West Nile encephalitis?

West Nile encephalitis (WNE) is caused by West Nile virus (WNV), a flavivirus previously only found in Africa, Eastern Europe, and West Asia. WNV is closely related to St. Louis encephalitis virus (SLEV) which is found in the United States and to the Japanese Encephalitis virus in South East Asia, the Murray Valley fever virus in Australia and New Guinea.

The majority of the people who get infected with the virus have no illness or at most, have an infection similar to a mild flu with fever, headache and fatigue. Rarely, will the virus multiply in the central nervous system and cause the brain disease called encephalitis.

How can I get it?

The principle route of human infection is through the bite of an infected mosquito.

In 2002, additional routes have become apparent, however this represents a very small proportion of cases. These routes include receiving transplanted organs and blood transfusions, transplacental and possibly breastfeeding transmission, and laboratory workers working with WN-infected products.

Who is most at risk?

People over 50 years of age have the highest risk of developing a severe illness because as we age, our bodies have a harder time fighting off disease. People with compromised immune systems are also at increased risk. However, anyone can get the virus.

What are the symptoms?

People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands, this is called West Nile Fever. People with more severe infections may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions and paralysis, this is called West Nile Encephalitis. If you have any of these symptoms, contact your doctor.

Are there long-term consequences?

While most infections are usually mild, West Nile Encephalitis can result in death or serious brain damage. Some improvements may be seen after some time.

Is there treatment or a vaccine?

There is no specific treatment for West Nile virus infection, nor a vaccine. While most people fully recover from the viral infection, in some severe cases hospitalization may be needed.

How can I protect myself?

It is not necessary to limit any outdoor activities, unless local officials advise you otherwise.

However, you can and should try to reduce your risk of being bitten by mosquitoes. In addition to reducing standing water in your yard, make sure all windows and doors have screens, and that all screens are in good repair.

If West Nile virus is found in your area:

* When outdoors, wear a mosquito repellent containing 20 -30% DEBT for adults and no more than 10% for children. Do not use repellent containing DEET on children under 3 years of age. Follow the label's instructions carefully, especially when applying to children. Wash all skin and clothing when returning indoors to remove insect repellent. Do not spray repellent in enclosed areas.

* Only adults should apply repellent on a child.

* Spray repellent on your hands and then apply to your face.

* Only apply repellent to exposed skin and clothing.

* After returning indoors, wash treated skin with soap and water.

* Do not use repellent under clothing.

* Wash treated clothing before wearing it again.

* Do not apply repellent over cuts, wounds, sunburn or irritated skin.

* Wear long-sleeved shirts and pants when outdoors for long periods of time.

* Avoid perfumes and colognes when outdoors for extended periods of time.

Remember, electromagnetic and ultrasound devices and Vitamin B are not effective in preventing mosquito bites.