Humanitarian Resource Institute:  A U.S. & International Resource on the Scope of Humanitarian Assistance

April 2001

Stephen M. Apatow
Director of Research and Development 
Humanitarian Resource Institute Emerging Infectious Disease Network
Eastern USA: (203) 668-0282   Western USA: (775) 884-4680


The introduction of West Nile (WN) virus in the northeastern United States during the summer and fall of 1999 raised the issue of preparedness of public health agencies to handle sporadic and outbreak-associated vectorborne diseases.

According to the Final Summary of the Year 2000 West Nile Virus (WNV) Outbreak, a total of 143 counties in 12 States and the District of Columbia had confirmed findings of WNV in a mosquito, bird, or mammal. The Centers for Disease control has now initiated a special West Nile virus surveillance program in 48 states and four cities 


West Nile Virus (WNV) Encephalitis Fact Sheet for Health Care Providers by the North Atlantic Regional Medical Command:

The mosquito-transmitted West Nile Virus causes West Nile Virus Encephalitis.  The virus was first reported in the United States in New York in the late summer of 1999.  Of 61 symptomatic cases, 7 died.

WNV Encephalitis is characterized by high fever, mental status changes, nausea, vomiting, a maculopapular  rash, and lymphadenopathy.  Interestingly, muscle weakness and paralysis were such prominent symptoms in some patients that they were considered to have Guillian-Barre Syndrome.  The disease is more severe in persons over fifty.  The overall mortality rate is 3% to 15%. 

In the Fall of 1999,  the New York Department of Health, in collaboration with CDC, conducted a door-to-door survey to determine how many people had been infected with West Nile virus in northern Queens. Based on these results, it is estimated that approximately 2.6% (or between 1.2% and 4.1%) of the population of age 5 or greater in the surveyed area in northern Queens (population 46,220) had been infected with West Nile virus (or between 533 and 1903 individuals). [Source:]

The total number of human cases in 2000 was 21, including 2 deaths: an 82-year-old man from Passaic County, NJ, and an 87-year-old woman from Kings County, NY.


In late August, more than 70 miles away in the Riverhead area of Long Island, 22 horses began showing neurologic signs of an encephalitic infection — lethargy, weakness in the hindquarters, and convulsions. Initially, local veterinarians suspected the horse deaths and illnesses were caused by equine protozoal myelitis. Later, on Oct 19, after 13 of the horses had died or were euthanatized, the USDA-APHIS announced they all tested positive for the West Nile virus. Horses are highly susceptible to the virus — a 1996 report from Egypt indicated 40 percent mortality.. - AVMA:Veterinarians key to discovering outbreak of exotic encephalitis. [Source:]

There were 60 equine cases of clinical illness due to infection with West Nile virus (WNV) confirmed by USDA-APHIS during the year 2000 in the United States. Of the 60 ill horses, 37 survived and 23 (38%) died or were euthanatized. Horses ranged in age from 4 months to 38 years, with an average age of 14.0 years; 36 cases occurred in male horses and 24 in females. Equine cases occurred in 7 different States. Onset of illness in the horses was from mid-Aug to the end of Oct. [2000].

During the year 2000, 6 wild mammals were classified as WNV-positive; 20 others are being evaluated by New York State to further characterize their WNV status.


Mosquito control is the most effective way to prevent transmission of West Nile and other arboviruses to humans and other animals, or to control an ongoing outbreak. Mosquito-control methods should include the following:

1. Mosquito abatement districts. The most effective and economical way to control mosquitoes is by larval source reduction through locally funded abatement programs that monitor mosquito populations and initiate control before disease transmission occurs. These programs also can be used as the first line emergency response for mosquito control if disease is detected in humans or domestic animals.

2. Public outreach. Public education about vectorborne diseases, particularly about modes of transmission and means of preventing or reducing risk for exposure, is a critical component of a prevention and control program.

Steps outlined by the Environmental Protection Agency to decrease mosquito populations include:

*  Empty standing water in old tires, cemetery urns, buckets, plastic covers, toys, or any other container where "wrigglers" and "tumblers" live.

*  Empty and change the water in bird baths, fountains, wading pools, rain barrels, and potted plant trays at least once a week if not more often.

*  Drain or fill temporary pools with dirt.

*  Keep swimming pools treated and circulating and rain gutters unclogged.

*  Use mosquito repellents when necessary and follow label directions and precautions closely.

*  Use head nets, long sleeves and long pants if you venture into areas with high mosquito populations, such as salt marshes.

*  If there is a mosquito-borne disease warning in effect, stay inside during the evening when mosquitoes are most active.

*  Make sure window and door screens are "bug tight."

*  Replace your outdoor lights with yellow "bug" lights.

*  Contact your local mosquito control district or health department. Neighborhoods are occasionally sprayed to prevent disease and nuisance caused by large mosquito numbers. If you have any questions about mosquitoes and their control, call your local authorities.


*  Stay indoors at dawn, dusk, and early evening. This is when the primary mosquito vector is most active.

*  Wear long-sleeved shirt, long pants, and socks whenever you are outdoors; wear loose-fitting clothing to prevent mosquito bites through thin fabric.

*  Use insect repellents that have been approved by the Environmental Protection Agency (EPA). They are safe and effective.

*  For your skin, use a product that contains 20-50% DEET (N,N-diethyl-meta-toluamide). DEET in higher concentrations is no more effective. Do not use DEET on infants (children under 3 years old).

*  Use DEET sparingly on children, and don’t apply to their hands, which they often place in their eyes and mouths.

*  Apply DEET lightly and evenly to exposed skin; do not use underneath clothing. Avoid contact with eyes, lips, and broken or irritated skin.

*  To apply to your face, first dispense a small amount of DEET onto your hands and then carefully spread a thin layer.

*  Do not inhale aerosol formulations.

*  Wash DEET off when your exposure to mosquitoes ceases.

*  For your clothing, use an insect repellent spray to help prevent bites through the fabric. Use a product that contains either permethrin or DEET. Permethrin is available commercially as 0.5% spray formulations.

*  Permethrin should only be used on clothing; never on skin.

*  When using any insect repellent, always FOLLOW LABEL DIRECTIONS.

*  For optimum protection, soldiers should utilize the DOD INSECT REPELLENT SYSTEM. In addition to proper wear of the battle dress uniform (BDUs), which provides a physical barrier to insects, this system includes the concurrent use of both skin and clothing repellents:

*  Standard military skin repellent: 33% DEET, long-acting formulation, one application lasts up to 12 hours.

*  Standard military clothing repellents, either: aerosol spray, 0.5% permethrin, one application lasts through 5-6 washes; or impregnation kit, 40% permethrin, one application lasts the life of the uniform.

Note: Vitamin B, ultrasonic devices, and ‘bug zappers’ are NOT effective in preventing mosquito bites.

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