The tiny buzz of doom

West Nile Fever fever pricks the Treasure Valley


You might be infected with the West Nile Virus. I might be infected with the West Nile Virus. If one is to believe local and national newscasts, we all—at least those degenerates and hussies among us who are depraved enough to wear anything less than full battle armor in the cool nighttime air—definitely carry the virus. But here's the stinger: most of us will never know if or when we have contracted the microorganism, will never feel the slightest twinge of illness and will henceforth become immune to any further WNV infection. Twenty-six times times more deaths occurred during a single 2003 French heat wave than have resulted from five American years of infection from the mosquito-derived encephalitis (brain swelling) that has become a household word for many Idahoans. But as Idaho's mosquito-friendly summer approaches, a now familiar refrain comes with it: Will this be the year that infected mosquitoes finally cross the divide from Montana, and start nibbling on Idahoan arms?

Boise's city government certainly seems to think so, as the city council voted last fall to allow all of Boise to be annexed by the Southwest Ada County Mosquito Abatement District (SWACMAD), an organization that has been eradicating nests in Eagle, Star and Kuna for 26 years but had yet to see a need to target Boise puddles and ponds. The reason for the change has as much to do with public appeasement as with fear of a viral epidemic. "As West Nile Virus continues its westward trek across the country more and more people have become keenly interested in mosquito abatement efforts," explains Carl Ellsworth, Environmental Manager for Boise City Public Works. "We are hopeful this public outreach campaign will provide people with the answers to their questions."

"If West Nile hits Boise then everybody is going to call us," adds Jack Bennett, head of the SWACMAD, "But we're trying to head that off as much as we can." But before descending into the SARS-esque world of mosquito net fashion, take heed to the statistics: Idaho's sole case of West Nile Fever, contracted by a Twin Falls County man from an imported alligator in 2003, was the only human instance yet to occur in the Pacific Northwest during the five-year American association with the disease. Even in Montana, a state with 222 reported cases and four deaths in 2003, WNV has still not crossed the western continental divide through infected bird hosts, but KTVB still declared to Boiseans in an April 30 headline, "West Nile Virus Coming to Idaho!"

Likewise, persistent use by the Center for Disease Control (CDC), as well as newscasts and papers of large maps with entire counties and states blacked in as "infected" could give the impression that large populations of people are in dire danger during a given year—an impression which WNV's mortality rates do not bear out. As of April 14, the CDC reports a total of 9,858 recognized cases of WNV infection in the U.S. in 2003—up from 4,156 cases in 2002. Of those 9,858 patients, 262 died—a mortality rate of 2.6 percent, or if one factors in the CDC statistic that only 20 percent of people who contract the virus ever become ill enough to recognize and/or report their particular affliction, a mortality rate of just over one half of a percent.

To take the analysis a step further, if the Montana Department of Health and Welfare's percentages of age distribution are taken to be fairly accurate—they report 91 percent of all fatalities occurring to patients over 65 years of age, which is by all media accounts a fair estimation—the chance of a healthy virus-carrying non-senior adult dying in 2003 of West Nile encephalitis or meningitis drops all the way below a half of a percent, or four one hundredths if the 80 percent non-recognition rate is counted. That rate is as low as influenza or pneumonia and lower than any acute strains of hepatitis—all of which have more confirmed cases in Idaho (265 influenza deaths in 2003, 1,061 cases of hepatitis A,B and C) than WNV over the last five years.

In addition Southwest Idaho, like New York and several large metropolitan areas, is in the middle of an full-fledged syphilis outbreak—24 cases in Canyon County in 2003 after 11 in 2002, according to Southwest District Health, and another 19 already in 2004 with well over a hundred more under investigation—but mosquitoes are still the plague du jour. The reason for the skeeter-skittishness, according to Dr. Leslie Tengelson, Department of Health Deputy epidemiologist, could have as much to do with WNV's capacity for stealth movement than for the virus's actual potential for harm. "West Nile is considered an 'emerging pathogen, which means that whether the attention is warranted or not, there is an element of the unknown in how it will move through the population," Tengelson explains, "although it does have some potential for fatal outcome, and we take it very seriously. Right now we have a high level of surveillance in Idaho, but we haven't found [the virus in migration] yet."

Statistics about the impact formal mosquito-abatement programs such as the SWACMAD have on the spread of WNV are unclear. Such programs play a prominent role in WNV-heavy states like Colorado, but the CDC reports that the amount of infected people in that state increased by over 2,000 cases in 2003 regardless. Tengelson reports having "antennae up" in veterinary, migratory bird and human health circles around Idaho to spot the first signs of WNV in Idaho, but expects our first non-alligator case to come from southern migration routes rather than over the continental divide. "We know now that it is in Southern California (25 confirmed human cases in 2003), so we might expect that it would hitch a ride with a bird that is migrating north on the western flyway. We might actually see it in Western Idaho before Eastern." Note the "mights": despite the hype, a ravaging of Idaho by the West Nile Virus in 2004 is by no means a foregone conclusion.