Ariz. struggles to call public’s attention to W. Nile threat

PHOENIX -- For many Arizonans, mosquitoes are like snow -- something they were glad to leave behind when they moved to the desert.

As a result, health officials are having a hard time getting people to focus on an outbreak of the West Nile virus even after the state declared a "serious public health threat" and laboratories diagnosed 232 cases of mosquito-related encephalitis and meningitis.

"We're afraid that people aren't buying it," said Will Humble, chief epidemiologist for the Arizona Department of Health Services.

Public concern was recorded as a collective yawn by a poll released July 21, showing that, despite official pleading, only 20 percent of residents surveyed had complied with requests that they check their backyards and neighborhoods for standing water where mosquitoes can breed. About 30 percent told the Rocky Mountain Poll in Phoenix that they had bought products with the mosquito repellent DEET, "but they use it just once or twice and forget about it," Humble said.

After identifying the chief source of the problem in neglected and abandoned swimming pools in Maricopa County, site of most of the West Nile cases, but not winning much public cooperation in cleaning the pools, the state took action. Its department of health authorized mosquito-fighting teams to enter backyards without the absent owners' permission and bomb suspicious pools with insecticides.

Meanwhile, the county called for backup. It arrived in the form of Gambusia affinis, a guppy that feeds on mosquito larvae. Maricopa officials are giving owners of stagnant swimming pools as many as a dozen specimens of each of this tiny, fast-breeding fish. The guppies devour all the larvae in a green pool within a day, according to Dr. Larry Jech, entomologist for the county, and the mosquitoes are not likely to return. That's because there will be 100,000 more guppies in the pool within a month.

Even with these interventions it is unclear whether health officials, without more help from the public, will stay ahead of the mosquito population.

At any given time, Humble estimates, 5 percent to 10 percent of the swimming pools in Maricopa County are abandoned outright or neglected to the point that they can breed mosquitoes. Even properly drained swimming pools can qualify as neglected in the Arizona summer just by collecting rain from the monsoon thunderstorms that march north into Phoenix from Mexico. The green sludge in these pools can produce from 10,000 to 100,000 adult mosquitoes every day.

That's not a lot compared with the visible swarms of millions of mosquitoes familiar to Easterners, entomologists say. And that is part of the problem. In the desert, there are too few mosquitoes to swarm human prey. They approach solo or in pairs, largely unnoticed until they bite. Keeping the public mindful of the mosquito danger "is kind of hard when you don't see them," Humble said.

But although the total number of mosquitoes in central Arizona is low, the rate of infection per mosquito is high.

Jech offered a comparison between Arizona, now in the outbreak's second season, which epidemiologists regard as usually the worst, and Colorado.

In the Rocky Mountain state in its second year, one of every 150 mosquitoes carried the virus. In Arizona now, Jech said, it's one mosquito in 10.

Two people have died from the West Nile virus in Arizona this year. About 80 percent of those who are bitten by an infected mosquito will not notice adverse effects. But the other 20 percent can suffer greatly from inflammation of the brain (encephalitis) or the membrane around the brain (meningitis).

Many of those who suffer most are older than 60, but not all. Former Phoenix mayor Paul Johnson, once known as "the boy mayor" for looking like the juvenile lead in a movie and even now barely past the threshold of middle age, came down with a rash, backache, headache, and other unpleasant symptoms before he was diagnosed with the West Nile virus. "To be honest," he told The Arizona Republic, "I thought since I had just turned 45, I was falling apart. I felt like there was a crowbar in the head splitting it open."