West Nile Virus Expected to Pose Strong Threat this Year

Since it was introduced into North America in 1999, most Americans are, by now, aware of the West Nile Virus. The mosquito-borne virus, which is traditionally seasonal in the U.S., has long been viewed as relatively mild – but one with potentially serious complications. This year, health officials are citing an increase in the more harmful aspects of the disease and are urging vigilance in keeping it at bay.

According to the Centers for Disease Control (CDC), symptoms of the West Nile Virus (WNV)  will not show up in approximately 80 percent of people bitten by an infected mosquito. About 20 percent of people who become infected will show mild symptoms, including fever, headache and body aches, nausea, vomiting and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have been sick for several weeks.

Additionally, serious WNV symptoms affect approximately 150 people annually. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These systems may last several weeks, and neurological effects may be permanent.

In 2003, 9,862 cases of WNV were reported to the CDC with 69 percent recorded as West Nile fever (the milder form of the disease) and 29 percent were reported as West Nile meningitis or encephalitis (more severe neuroinvasive disease). Two percent were clinically unspecified. This is more than twice the level of outbreak from 2002 when a total of 4,156 cases were reported.

However, the number of reported cases dropped dramatically in 2004 with only 2,740 human cases reported. Still, one third of those cases (900 cases) were severe in nature and health officials worry that could increase this year. Moreover, it’s not just the young and elderly who are at risk. Healthy individuals in their 30s, 40s and 50s have been contracting West Nile Virus more readily in recent years.

"West Nile is fading a little bit from the public consciousness," worries Dr. Henry Masur of the National Institutes of Health in a report by the Associated Press. "Still, there are more cases of paralysis (from West Nile) than there were in many years of polio."

According to the Associated Press, in a study to be published in July, the CDC’s Dr. Jim Sejvar estimates that 10 percent of people who develop the most severe West Nile disease may have some degree of the polio-like complication and many don’t recover muscle function. Even the less serious form of illness, West Nile fever, is turning out to be harder to kick than doctors initially described, so much so that the CDC has largely abandoned it’s earlier characterization as a “mild disease.”

With no vaccine, CDC and other health professionals note that the best protection against WNV is to avoid mosquitos as much as possible. This may be difficult for lawn and landscape contractors who spend the majority of their time outdoors. Still, the CDC offers the following tips for keeping relatively bite-free in the coming mosquito season:

Apply Insect Repellent Containing DEET (N,N-diethyl-meta-toluamide) to exposed skin when you go outdoors. Even a short time being outdoors can be long enough to get a mosquito bite. Mosquitoes that carry the West Nile Virus are most likely to bite around dusk and dawn, so wearing repellant during these times of day is especially important, though the safest decision is to apply repellant whenever you are outdoors. Follow the directions on the product you’re using to determine how frequently the repellant must be reapplied. Sweating, perspiration or getting wet may require you to reapply more frequently. Repellants containing a higher concentration of DEET provide longer lasting protection.

Clothing Can Help Reduce Mosquito Bites. When possible, wear long-sleeves, long pants and socks when outdoors. Mosquitoes may bite through thin clothing, so spraying clothes with repellent containing permethrin or DEET will give extra protection. Don't apply repellents containing permethrin directly to skin. Do not spray repellent containing DEET on the skin under your clothing.

Be Aware of Peak Mosquito Hours. As mentioned, the hours from dusk to dawn are peak mosquito biting times for many species of mosquitoes. Take extra care to use repellent and protective clothing during evening and early morning, or consider avoiding outdoor activities during these times.

Drain Standing Water. Mosquitoes lay their eggs in standing water. Limit the number of places around your home, your facility or your clients’ homes for mosquitoes to breed by getting rid of items that hold water. Moreover, if your company installs or maintains water features, ensure that the pumps and filters are working properly so water is circulated effectively and isn’t stagnant. This can become a lucrative add-on service in the summer, as well as making other suggestions to clients, such as adding pond fish that eat mosquitoes to water features.

Report Dead Birds to Local Authorities. Mosquitoes don’t just bite people. Dead birds may be a sign that West Nile virus is circulating between birds and the mosquitoes in an area. More than 130 species of birds are known to have been infected with West Nile virus, though not all infected birds will die. It's important to remember that birds die from many other causes besides West Nile virus. By reporting dead birds to state and local health departments, you can play an important role in monitoring West Nile virus. State and local agencies have different policies for collecting and testing birds, so check the Links to State and Local Government Sites page on the CDC Web site to find information about reporting dead birds in your area.