Ask the Doctor

West Nile Virus

I have heard that this season is predicted to be an especially bad one for West Nile Virus. What are the symptoms of West Nile Virus infection and what can I do to protect my children?

West Nile virus is transmitted through the bite of infected mosquitoes. Mosquitoes become infected when they feed on infected birds. The virus resides in the mosquitoes’ salivary glands where it may be transmitted during subsequent bites to humans and animals. Once the virus has been injected it may multiply causing illness. The virus has not been shown to be transmitted directly from dead birds to humans, but it is recommended that direct contact with dead birds be avoided. West Nile cannot be transmitted through person to person or person to animal contact. There has been one reported case of maternal-fetal transmission in which the infection passed through the placenta.

The vast majority of people bitten by mosquitoes that are carrying the West Nile virus do not become ill. Only 20% of infected persons develop any noticeable symptoms and less than 1% of infected people develop severe infection. Symptoms of mild disease (West Nile fever) include fever, headache, fatigue, swollen lymph glands and occasionally a skin rash on the trunk of the body. Symptoms of severe infection (West Nile encephalitis or meningitis) include high fever, lethargy, severe headache, stiff neck, weakness, convulsions, coma and paralysis. These more serious symptoms are due to meningitis -inflammation of the meninges, which are the membranes surrounding the brain and spinal column, or encephalitis – inflammation of the brain tissue itself. Persons with symptoms consistent with mild disease should be monitored for the development of more serious symptoms, the presence of which should prompt consultation with a physician or other health care provider.

The incubation period for West Nile virus infection is usually 3-14 days and in mild cases, symptoms may only last for a few days. In more severe cases symptoms may persist for weeks and require hospitalization for supportive care such as IV hydration and respiratory support.

For people residing in endemic areas, where West Nile virus has been reported, taking measures to prevent mosquito bites are the best defense against illness.

• Avoid being outdoors at dawn or dusk when virus carrying mosquitoes are most prevalent
• Wear protective clothing –light colors are best so you can see a mosquito if it lands and thicker weaves are more protective than thin fabrics which may be bitten through
• Rid areas of stagnant, standing pools of water which may serve as breeding grounds
• Use DEET containing insect repellents
• Use net covers on strollers and infant seats

Insect repellents containing DEET are the best-studied and most effective products available. The concentration of DEET relates to the duration of effectiveness.

• 23.8% DEET provides approximately 5 hours protection
• 20% DEET provides approximately 4 hours protection
• 6.65% DEET provides approximately 2 hours protection
• 4.75% DEET provides approximately 1.5 hours protection
  Of note, non-DEET containing cosmetic or natural products such as Skin-So-Soft and 2% soybean oil provide a minor degree of protection similar to that of 4.75% DEET.

There are no definitive studies regarding the use of DEET in infants and children, however, the American Academy of Pediatrics reports that products containing 30% DEET appear to be as safe as 10%, as long as they are properly applied. While the best measures are avoidance, insect repellent may be used for infants and children over two months of age who are likely to be exposed to infected mosquitoes. Repellent may be applied to clothing and or skin (but if clothing is sprayed, don’t apply to underlying unexposed skin). Repellant should be applied to the adult’s hands and then carefully applied to the child’s skin avoiding eyes, mouth and hands if the child is likely to put his/her hands in mouth. Choice of product should be dictated by duration of protection required and the age of the child. Skin should be washed and clothing should be changed immediately after coming inside in order to minimize exposure.

Information obtained from CDC and AAP sources
For more information visit www.cdc.gov

May 12, 2004

Copyright© 2004, K. Coleman, L.L.C., all rights reserved.