Mosquitoes are expected to bring a new, deadly disease to Arizona this summer, according to local disease control experts.
The threat is prompting officials in Queen Creek, with its many irrigated fields, and Maricopa County officials to step up efforts to control the insects that spread the disease.
The West Nile virus spread as close as New Mexico and Colorado last year, said John Townsend, vector control manager for the Maricopa County Department of Public Health. It killed 277 Americans, according to the federal Centers for Disease Control and Prevention.
Based on the rate at which West Nile has swept across the country since it first appeared in New York in 1999, the encephalitis-causing strain is almost certain to reach Arizona this year, Townsend said.
"We expect it to probably hit this summer sometime," he said.
Arizona's elderly are particularly at risk, Townsend said, because West Nile is much more likely to kill adults age 70 and older.
West Nile is a more aggressive virus than the other leading mosquito-borne illnesses, western equine encephalitis and St. Louis encephalitis. Fortunately it is also easier to spot, Townsend said, because it leaves a trail of dead birds in its wake.
With the forms of encephalitis already spotted in Arizona, birds' blood serves as a reservoir for the disease, which can cause deadly swelling of the brain. But the birds are not visibly affected by it, he said. "With West Nile, a lot of the birds die. West Nile actually kills the birds."
In the East Valley, Queen Creek is the top breeding ground for mosquitoes that could carry West Nile, Townsend said. The town's many irrigated fields and drainage ditches are tailor-made for larvae to thrive.
"Those tend to put off what we call floodwater mosquitoes," Townsend said. "These are the really aggressive mosquitoes."
In anticipation of this year's mosquito season, which usually runs May through October, the Queen Creek Town Council approved funding Tuesday night for a plan to educate residents about the mosquito problem and attack potential breeding grounds with larvacide and bug-killing mist.
Beginning this month, Maricopa County also will boost public education efforts and begin testing for West Nile and other viruses.
Townsend said it is likely that West Nile would first be detected in the county's "sentinel chickens," which live in strategic areas around the county and are tested regularly for disease. The chickens do not die from encephalitis, but they do develop antibodies that can be traced in blood samples.
The birds most likely to die from West Nile are those in the corvid family, which includes grackles, sparrows, finches and ravens. Beginning in May, Maricopa County residents will be able to call the county's environmental health complaint line at (602) 506-6616 to report any fresh, dead birds that are candidates for West Nile.
Birds that have been dead for several days, pigeons (which appear to be immune) and baby birds (which already have a high mortality rate) are excluded from the tests, said Craig Levy, vector-borne disease program manager for the Arizona Department of Health Services.
"People shouldn't be offended if we don't test their bird," he added.
ADHS also will have a hotline for up-to-date information about West Nile at (602) 364-4500, and its Web site will include a map showing areas where the disease is detected, at www.hs.state.az.us.
"It's going to be an interesting year," Levy said. "I just hope it's later rather than sooner."