West Nile Virus Invades Arizona

Arizona Nurse, Sep 2004 by Denious, Andie

West Nile Virus (WNV) is a term that wasn't even part of our vocabulary just a few short years ago, but now we hear it daily. Well, just what is WNV, where did it come from, how does it affect us, and what can/should we do to prevent its spread?

Prior to 1999 when the first case of WNV was documented in the United States (New York City area), WNV was found only in parts of Africa, the Middle East, and Asia. Since that first case in 1999, WNV has rapidly spread across the U.S. by infected birds that transmit the virus to mosquitoes. When mosquitoes bite infected birds, the mosquitoes become infected and transmit the virus to humans during blood meals (when they bite). Horses are also infected with WNV after being bitten by infected mosquitoes. Horses can be vaccinated yearly to avoid infection. Dogs and cats are not susceptible to WNV.

Most people (approximately 80%) who become infected exhibit no symptoms at all. Others may develop mild symptoms including fever, headache, body aches, nausea, vomiting, swollen lymph glands or a rash on the chest, stomach and back. The incubation period is from 3-14 days after being bitten. The symptoms usually last for a few days depending upon the severity of the disease. Fewer than 1 out of 100 people develop more severe symptoms that require hospitalization. Severe symptoms would include headache, high fever, stiff neck, mental confusion, muscle weakness, tremors, convulsions and paralysis, and in some cases, particularly in older individuals, death can result. Persons who contract WNV seem to develop immunity to the disease that is assumed to be lifelong, although the immunity may wane in later years. Since WNV is an emerging disease it is uncertain what long term effects may be at this time.

Individuals (all age groups) most at risk for WNV infection are those who spend a lot of time outdoors. Although everyone is at risk of getting infected, individuals over the age of 50 are at higher risk for severe illness and death. As with most diseases, prevention is the best way to avoid becoming infected. Although two drug companies are currently testing vaccines against West Nile, it is uncertain if the vaccines will be further developed at this time. Therefore, the most effective and practical way to greatly reduce your chance of contracting WNV infection is to follow the CDC recommendations listed below:

As with most diseases, prevention is the best way to avoid becoming infected.

* At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, and cans.

* Check for clogged gutters and clean them out.

* Remove discarded tires, and other items that could collect water.

* Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.

* When possible, wear long-sleeved shirts and long pants whenever you are outdoors.

* Place mosquito netting over infant carriers when you are outdoors with infants.

* Consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times. The mosquitoes to worry about are night biters.

* Install or repair window and door screens so mosquitoes can't get indoors.

* Use enough repellent to cover exposed skin or clothing. Do not apply repellent to skin under clothing. If repellent is applied to clothing, wash treated clothing before wearing again.

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

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

* Do not spray aerosol or pump products in enclosed areas.

* Do not apply aerosol or pump products directly to your face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.

* When using repellent on a child, apply it to your own hands and then rub them on your child. Avoid children's eyes and mouth and use it sparingly around their ears.

* Do not apply repellent to children's hands. (Children may tend to put their hands in their mouths).

* Do not allow young children to apply insect repellent to themselves; have an adult do it for them. Keep repellents out of reach of children.

Products containing DEET come in different strengths. You should choose a repellent that provides protection for the amount of time you would be outdoors. Follow the directions for the product you are using. Sweating, perspiration and getting wet may mean you need to reapply repellent. If you aren't being bitten, you don't have to reapply repellent. The concentration of DEET products range from less than 10% up to 50%-30% is the maximum concentration recommended for infants (2 months and older) and children. The concentrations listed on the next page provide guidelines for what strength should be used depending on the length of time you will be outdoors:

* A product containing 23.8% DEET provides an average of 5 hours protection

* A product containing 20% DEET provides an average of 4 hours protection

* A product with 6.65% DEET provides almost 2 hours protection