West Nile Virus is Here to Stay
by Fleet Surgeon Gail Bowdish, MD, FACEP
During 2002, we saw an increase in the incidence of West Nile Virus infections in humans, and every indication is that this disease is here to stay. West Nile Virus causes an illness that is transmitted by mosquitoes. The good news is that most people who are bitten by infected mosquitoes will not have any symptoms, or if they do become ill, they will experience a mild illness and may not even be aware that they have the disease. People over the age of 50 and those with poor immune systems are at the greatest risk of serious illness.
It is estimated that 20% of the people who become infected will develop West Nile fever: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands.
The symptoms of severe infection (West Nile encephalitis or meningitis) include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that 1 in 150 persons infected with the West Nile virus will develop a more severe form of disease.
The bad news is that we saw the highest incidence of serious illness and death in the Great Lakes region. The following numbers were reported in 2002: Illinois 879 cases and 60 deaths; Michigan 614 cases and 51 deaths; Ohio 441 cases and 31 deaths; Ontario 389 cases and 17 deaths; Wisconsin 52 cases and 3 deaths; Minnesota 48 cases and no deaths.
More good news is that West Nile Disease is preventable. Avoid mosquito bites to prevent infection. Mosquitoes breed in the water, and as boater's we are certainly not going to avoid the water. But we can reduce our exposure to mosquitoes by checking and repairing the screens on our boats, or by draping mosquito netting over opening ports, especially during dusk and dawn which are the prime feeding times for mosquitoes.
Wear long sleeved shirts, long pants and socks. Apply insect repellent containing DEET (N,N-diethyl-meta-toluamide) to exposed skin whenever you are outdoors. Treating clothes with repellents containing permethrin or DEET will give extra protection, since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to skin. Do not spray repellent containing DEET on the skin under your clothing. Wash repellant from your skin when protection is no longer needed.
A recent study showed that a higher percentage of DEET in a repellant provided increased length of protection, but that concentrations higher than 50% do not increase the length of protection.
" A product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites.
" A product containing 20% DEET provided almost 4 hours of protection
" A product with 6.65% DEET provided almost 2 hours of protection
" Products with 4.75% DEET and 2% soybean oil were both able to provide roughly 1 and a half hour of protection.
Choose a repellent that provides protection for the amount of time that you will be outdoors. A higher percentage of DEET should be used if you will be outdoors for several hours while a lower percentage of DEET can be used if time outdoors will be limited. Re-apply after getting wet or perspiring.
You can also re-apply a product if you are outdoors for a longer time than expected and start to be bitten by mosquitoes.
West Nile Virus may be here to stay, but we can still enjoy our time on the water this summer. Just remember to pack the insect repellant and don't forget to use it. See you on the water.