You settle, sighing with righteous pleasure, into the lounger on your deck to enjoy the velvet evening air. The breeze rises; it carries the moist rich scent of nearby wetlands while the croak of frogs vies with the hum of insects in the gloom.

       You listen a moment before reaching for the bottle on the table. No, not the one containing your favorite potent potable – you want the other bottle. The spray can with the picture of picnickers enjoying the outdoor life. The elixir used to provide protection from the scourge of mankind. The one with the magic ingredient called DEET.

       The mosquito, ubiquitous to most of the world, transmits malaria, yellow fever, dengue fever, and "St. Louis" encephalitis – among others. These diseases did what distance, expense, climate, and defenders could not in limiting England’s colonial expansion, for bringing the French ditch-diggers to their knees in Panama, for decimating the Northern armies in the Civil War, for further weakening the already under-supported and vilified American soldiers of the Vietnam Conflict, and for the abandonment of the first towns of the Louisiana delta and the Virginia tidewater regions. The tiny pest is now responsible for the newest disease to hit the New World.

       West Nile Fever is a form of viral infection that usually causes flu-like symptoms in humans. Occasionally, in less than one percent of all victims, the virus crosses the meninges (the brain/blood barrier) and causes a swelling of infected tissues known as meningitis or encephalitis. A few of those afflicted will die, especially the elderly.

       The disease was first identified in Uganda in a middle-aged woman of the West Nile region. Outbreaks occurred in Egypt, Israel, and southern France. The pattern of the spread of the disease matches the migration paths of several species of birds that winter in Africa. The infected birds travel to their destination and are bitten by local mosquitoes that, in turn, pass the disease to other birds, house pets, horses, and humans.

       Old World bird carrier species of the virus do not seem susceptible to the effects of the disease, unlike New World birds. Here in the U.S., wide spread crow and sparrow deaths have accompanied the human outbreaks. The strain is virtually identical to the type found in the Middle East, which is different from the West African variety. It is likely that storm-tossed migratory birds or illegally imported domesticated species may be the vectors responsible for introducing the virus to our shores.

       New York City, with its long history of welcoming immigrants, was the site of the first New World outbreak in 1999. Unfortunately, for the residents of the northern states, the virus appears to be quite at home wintering with hardy types of mosquito and local winter bird species.

       Additional cases - and the rare fatality - have surfaced in New Jersey, Pennsylvania, Maryland, and other eastern seaboard states, and are now gradually moving south into the more hospitable climate of Dixie.

       The complete integration of the virus awaits three key factors: an infectious host bird with the potent virus in his blood; active, bird-loving mosquitoes; and large numbers of bird species to amplify, or spread, the initial contact. When the spring migration arrives these infected birds – those asymptomatic or otherwise healthy enough to fly – will carry the virus to their summer breeding grounds and all the landings between. The virus will take hold in those new places if the above-mentioned conditions are met.

       Early intervention is the best hope for averting this frightening scenario.

       Veterinary and human medical personnel need to be aware of the nature of the symptoms, the availability of diagnostic blood tests, and treatment. Not every bite results in an obvious infection - the contagion rate is less than 1%. The incubation period, or time between infection and symptoms, is usually 3 to 15 days. Symptoms, in humans, include fever, headache, body aches, skin rash, and swollen glands. More severe cases present with worsening of these symptoms, with neck stiffness, tremors, disorientation, muscle weakness, stupor, paralysis, coma, convulsions, and, rarely, death.

       Treatment is supportive of symptoms only. Complete recovery is the normal course. There are no known effective anti-viral compounds at this time. One British biotech firm, Acambis, is in the testing phase of a vaccine. Human trials are scheduled for 2002.

       The intermediate hosts cannot transmit the disease directly. The bite of a mosquito seems to be a necessity to infection, but suspect animals and their blood should be handled with gloves. The carcasses should be double bagged and discarded in a closed can. Although the chances of cross-contagion are slim, infected animals and people should be quarantined and protected from further mosquito bites. Horses are especially at risk for the more virulent symptoms but with prompt and appropriate treatment usually recover. Dogs and cats are only rarely affected but may carry the virus.

       Widespread bird flock deaths should be reported to public health officials or the CDC (Center for Disease Control), who will investigate. Don’t send them dead birds. The virus doesn't remain viable long and will not be detectable in the corpses.

       The prevention is the standard one for mosquito-borne pathogens; limit breeding grounds by eliminating stagnant pools of water. Old tires, hubcaps, buckets, paint cans, inverted Frisbees, forgotten children's toys, abandoned barrels, and other items capable of holding reservoirs of rain are prime mosquito breeding sites. Neighborhoods should organize clean up and disposal of such debris. Empty and refill birdbaths regularly, overturn decorative pots after storms, and maintain rain-gutters free of leaves and other obstacles that may allow puddles to form.

       Personal protection can be best achieved by avoiding dense undergrowth and marshes, choosing loose-fitting long-sleeves and pants for evening outdoor activities, and using insect-repellent containing DEET. Herbal mixtures, bug-zappers, and citronella offer spotty protection at best, and shouldn’t be relied upon completely. If DEET is not an option due to allergies or health concerns, avoiding outside activities during the prime mosquito hours of evening is an alternative.

       Shooting crows, banishing house pets, and destruction of livestock are not reasonable or helpful courses of action. Keep the cat. Get rid of the mosquito. Enjoy the outdoors prepared. Don't give up your favorite pastimes. Swim and boat in fresh water in the warm weather. Avoid marshes and stagnant standing pools. Act sensibly, but don't over-react.

       After a hard day on the job, that frosty mint julep, cold bottle of Ice-House, or tall Long Island ice-tea may be the cure for what ails you, but the lowly can of OFF or Cutter is more likely to ward off the pesky mosquito…

       Giving you one less ailment to worry about.

References:

NYC West Nile Information Site

CDC West Nile site

search: West Nile – The Florida Times-Union

Medical Laboratory Observer – August 2001

The Intelligencer Journal – Harrisburg (AP) Thursday, August 2, 2001