Experts predict the continued spread of West Nile virus
this summer, with the potential for serious outbreaks in numerous states, including California. Last year 9,858 human cases were reported to the federal Centers for Disease Control and Prevention—more than double the 2002 total of 4,156—with 258 deaths. West Nile first emerged in the United States in New York in 1999, when reported cases totaled 62. Since that time, the virus has moved relentlessly westward and southward, spread by migratory birds. Mosquitoes acquire the virus when they bite infected birds and then transmit it to humans.
University of Florida Professor Jonathan F. Day, Ph.D., a medical entomologist specializing in tracking mosquito-borne illnesses including West Nile, says the virus will continue its spread and may re-emerge in regions where it has been present, but not in epidemic proportions, as it was in previous summers.
“We are very concerned about having a large number of cases in California,” Day said. He added, “The Southeast has not seen a major epidemic of West Nile since the virus was first introduced, and southeast Florida from Miami to Vero Beach is particularly at risk for a major spread of the disease if the weather conditions are right.” Day and other experts are also carefully monitoring Texas, where a high case count is possible. He suggests that disease incidence in the Northeast may be higher than in the past few years and is particularly concerned about the Delaware River Valley. “This is an area that traditionally has many mosquito-related illnesses, so we think it’s a possibility for significant West Nile activity this year.”
Lyle R. Petersen, M.D., M.P.H., director of the Division of Vector-Borne Infectious Disease in the CDC’s National Center for Infectious Diseases, agrees that the disease could have a big impact again this year. “We’ve had two very large outbreaks, both in 2002 and 2003, and there’s no reason to believe that 2004 will be any better,” he says. “The best way to avoid West Nile Virus is to avoid being bitten by mosquitoes,” he says, adding, “The best way to do that is to wear insect repellents that contain DEET. These are the most effective repellents.” He also recommends wearing long sleeves or long pants to provide a barrier against mosquito bites and being especially cautious about protective measures at dawn or dusk when mosquitoes that carry West Nile virus are most likely to be active.
West Nile Can Cause Serious Illness in Individuals of All Ages
West Nile infections tend to be more serious in older adults, but the disease’s potential for greatly impacting even young, vigorous individuals was highlighted last year. Petersen knows this first hand. He lives in Colorado, last year the nation’s hardest hit state with 2,947 human cases of West Nile, including 63 deaths. Colorado had more than a third of all of the reported West Nile illnesses in the nation last year.
Petersen was among those who became ill, contracting the virus when he ventured outside at dusk to retrieve his family’s mail. He was not wearing insect repellent and stopped to chat with a neighbor outdoors for more than 30 minutes. Numerous mosquitoes bit Petersen—at least one carrying West Nile virus—and symptoms appeared with a vengeance three days later. His case was officially classified as “mild,” a designation Petersen says does not properly characterize the disease. He was confined to bed for a week and ill for several more weeks.
“This classification has lulled many individuals into thinking that West Nile isn’t that serious,” he says. “I can tell you from experience that you don’t want to get this virus. It is anything but mild.”
This sentiment is echoed by other Coloradans—previously healthy 20-, 30- and 40-somethings— who became ill. Greeley resident Tom Weber, 46, was hospitalized for nearly eight months. He had been an athletic outdoors enthusiast who skied and played in adult amateur basketball and hockey leagues.
“For me, the symptoms of West Nile disease came on quickly,” says Weber, released from the hospital late last month. “I had paralysis throughout my body. I still have some on my right side.” On a respirator during much of his hospital stay, he suffered a heart attack, pneumonia, and other effects. “It really turned my world upside down,” he says. His weight dropped from 220 to 160 pounds.
Another 46-year old Greeley resident, Sharon Carey was also hospitalized with West Nile in 2003. She says: “I never thought something like this would ever happen to me. I’ve had mosquito bites all my life and they had never caused anything serious. My message is that West Nile virus can affect anybody at any age. You wouldn’t want this disease.”
Evan Young, 21, a college student and football player from Fort Collins, was seriously ill last year with West Nile virus and was unable to leave his bed for two weeks with back and leg pain. He still has some lingering effects but has otherwise recovered. He describes his illness as “terrible.”
Preventing Mosquito Bites, Possible West Nile Infection
DEET-based insect repellents are recommended by the federal Centers for Disease Control and Prevention, as well as by state and local public health agencies, to help protect against mosquito bites that may transmit West Nile. The CDC says that DEET-based repellents “are very safe” when used according to label directions. The American Academy of Pediatrics says “Products containing DEET are the most effective mosquito repellents currently available” and suggests that repellents containing up to 30 percent DEET can be used to help protect against insect- and tick-borne disease for children two months of age or older.
Scientific research, particularly a study published in the New England Journal of Medicine in July 2002, demonstrates that DEET is the most effective personal-use insect repellent ingredient available. It has been studied extensively by scientists and healthcare professionals since its introduction in1957. The industry estimates that about one-third of Americans use DEET-based products every year.
DEET-based repellents are also effective in helping to prevent tick-borne diseases such as Lyme disease, which is expected to hit a record high in the United States this summer, and Rocky Mountain spotted fever, which is sometimes fatal, even among teens and children.
“As with any product, read and follow label directions when using DEET-based repellents,” says Susan Little, executive director of the DEET Education Program, which operates under the auspices of the Consumer Specialty Products Association. She recommends that parents or other caregivers apply repellents on younger children (rather than letting them do this themselves), avoiding the child’s lips, mouth and eyes. “Apply only to exposed skin, not under the child’s clothing,” she says, “and do not apply insect repellent to a very young child's hands, since these youngsters often put their hands in their mouths or rub their eyes.”
The higher the concentration of DEET in a repellent formulation, the longer the product will ward off the biting insects. Lower concentration products are adequate when exposure to biting insects and ticks is brief. Use higher concentration products for longer outdoor periods and/or when populations of mosquitoes or other biting pests are high. “If the humidity is high and/or it’s very hot, more frequent applications may be needed, since perspiration washes the repellent from the skin,” Little says.
For more information about using repellents, along with other recommendations for helping to prevent insect and ticks bites, visit http://www.deetonline.org. To order free educational brochures in English or Spanish, call toll-free telephone line: 1-888-No-Bites (662-4837).