West Nile Virus
West Nile Virus in Oklahoma Mosquito Season 2006
Q: How do people get infected with West Nile virus (WNV)?
A: The most likely route of human infection with WNV is through the bite of an infected mosquito. Some people have also become infected with the virus following receipt of contaminated blood or blood products, or transplanted organs from an infected donor. Mothers who are recently infected with WNV may also transmit the virus to their unborn child, or to their baby while breastfeeding.
Q: If I live in an area where birds or mosquitoes with West Nile virus have been reported and a mosquito bites me, am I likely to get sick?
A: It only takes one bite from an infected mosquito to transmit the disease, however, even in areas where the virus is circulating, less than 1% of mosquitoes are generally infected with the virus. Therefore, the chances you will become severely ill from any one-mosquito bite are extremely small. Persons who have repeated exposures to mosquitoes are at higher risk of acquiring West Nile disease.
Q: What are the symptoms of West Nile virus infection?
A: Most people who are infected with WNV will not have any noticeable illness, or have a milder form of West Nile disease called West Nile Fever. Persons with West Nile Fever typically experience symptoms of fever, headache, nausea, muscle weakness, and body aches lasting 2 to 6 days or longer. Sensitivity when looking at light and a skin rash appearing on the trunk of the body may also be present.
Approximately 20% of persons infected with WNV will develop more severe neurologic disease that may be life-threatening. Adults over the age of 50 years old are at greater risk of having serious disease. Potential symptoms of severe infection (West Nile encephalitis or meningitis) include intense headache, dizziness, severe muscle weakness, neck stiffness, vomiting, disorientation, mental confusion, tremors, muscle paralysis, or convulsions and coma.
Q: What is the incubation period in humans (i.e., time from exposure to onset of disease symptoms) for West Nile encephalitis?
A: Usually 3 to 15 days.
Q: How can I reduce my risk of getting West Nile disease?
A: Practice the four “Ds”!
· Apply a mosquito repellant containing DEET or another approved active ingredient such as Picaridin or oil of lemon eucalyptus.
· Avoid being outdoors between Dusk and Dawn.
· Drain any standing, stagnant water observed in containers or artificial locations around your home and workplace.
· Dress wearing long sleeves and long pants to shield skin from mosquitoes.
. Prevent items such as buckets and tarps from holding standing water.
. If rainwater is collected, cover and seal containers when not collecting rain.
. Empty your outdoor pet’s water bowl and refill daily.
. Rinse, scrub, and refill birdbaths weekly.
. Empty plastic wading pools weekly and store indoors when not in use.
. Regularly maintain swimming pools and outdoor hot tubs.
. Store boats covered or upside down.
. For a water garden or ornamental body of water, use an environmentally safe product to kill the larvae, e.g. BTI, or stock with fish that eat mosquito larvae.
. Regularly clean fallen leaves and debris from roof gutters.
. Trim grass and weeds and dismantle brush to deprive mosquitoes of a habitat.
. Repair or replace all broken or torn window and door screens.
. Repair leaky lawn irrigation spouts.
Q: What is “DEET” and how often should I use it to repel mosquitoes?
A: DEET is the shortened acronym for the chemical N,N-diethyl-m-toluamide which is the active ingredient found in most insect repellants that are safe to apply to the skin. Before buying a mosquito repellant, check the label for this chemical name and look at the concentration. DEET-containing repellants are available in concentrations ranging from 4% to 100%. Higher concentrations do not work better, they just last longer. For most outdoor activities, using a 10%-30% product is adequate.
The most effective repellents contain active ingredients of DEET (N,N-diethyl-m-toluamide) or Picaridin (KBR 3020) which repel pests like mosquitoes and ticks. Repellents containing these ingredients have been tested against a variety of biting insects and has been shown to be very effective. Oil of eucalyptus [p-methane 3,8-diol (PMD)], a plant based repellent has been shown to provide similar protection to lower concentrations of DEET. Always follow label directions when applying repellant.
Information About WestNile
Oklahoma State Department of Health web site at: //www.health.state.ok.us/program/cdd/ow/index.html for current updates on West Nile virus activity and state surveillance results.