Just as the flu season is winding down, mosquito season and the West Nile virus are ramping up. And in case evenings on your patio haven’t convinced you, state and county health officials confirm that the pesky bloodsuckers are breeding faster than rabbits.
The state’s first West Nile-positive mosquitoes were confirmed Friday in a batch from Clarkdale in Yavapai County, an early start for the cooler climes.
So West Nile in the East Valley can’t be far behind.
“We’ve had some pretty heavy rains. That’s creating backyard breeding,” said Craig Levy, head of the Arizona Department of Health Services’ vector-borne and zoonotic diseases section.
“That’s probably why we’re noticing mosquitoes a little earlier than usual.”
Maricopa County workers are checking traps at about 500 locations, and haven’t found a West Nile-positive mosquito yet, said John Townsend, manager of the county’s vector control program.
But traps in Gilbert, Tempe, east Mesa and elsewhere are collecting hundreds of Culex mosquitoes, the variety that most commonly carry the deadly West Nile virus. Just 30 Culex mosquitoes in a trap is enough to get trucks dispatched to the neighborhood for insecticide fogging and possible larvicide treatment.
“We’re starting to see the numbers climb up a little bit,” said Townsend, whose office is fielding 200 to 300 complaints a week.
Some communities, such as Gilbert, augment the county’s mosquito control efforts with their own. Twice a week, from April to October, neighborhoods adjacent to Gilbert parks and in flood irrigation areas are fogged.
“We got a lot of complaints from people who live around areas that get flood irrigation,” said Gilbert wastewater superintendent Mark Horn.
Levy said he was getting eaten alive in his backyard until he discovered the source: a neighbor’s untended pool. Once the pool was cleaned up, Levy’s mosquito problem was solved.
“Being a little nosy may not be a bad thing,” Levy said. “If you’ve got a problem, you need to find the source.”
The county has stepped up efforts to fine green-pool owners, and it issues dozens of citations each month.
Last year, it was late June before the first West Nilepacking mosquitoes were confirmed, and they were in La Paz County. By October, the virus had infected 150 people and killed 11 of them, including six in Maricopa County. That put Arizona fifth in the country in the number of 2006 West Nile fatalities.
In 2005, there were 106 human cases and four deaths; and 391 cases, with 16 deaths, in 2004.
Most people bitten by infected mosquitoes won’t develop any symptoms, about 20 percent will develop flulike symptoms, and fewer than 1 percent develop encephalitis. Those most at risk are the elderly and people with compromised immune systems.
As if the West Nile virus weren’t enough, Arizona health officials are watching the surge of dengue fever in Latin America. Cases of the deadly hemorrhagic form have increased by more than 600 percent in Mexico since 2001 according to a recent report, and experts here worry it will continue to spread north.
Townsend said the vector for dengue fever — the Aëdes aegypti mosquito — has been buzzing around Tempe since at least 2000. Researchers in Tucson have been watching the mosquito and working with counterparts in Mexico to try to understand and control its breeding there.
The black mosquito with white-spotted legs can breed in just a teaspoonful of standing water. It prefers people to pets and nibbles from the kneecaps down, earning the name Aëdes aegypti, or “ankle biter.”
“They’re a tropical mosquito. Normally in the desert, they’d just dry up and die,” Townsend said.
Eight Valley residents were stricken with dengue fever last year during a missionary trip to the Domincan Republic, he said. Four were hospitalized.
So far, there have been no locally acquired cases of dengue fever.
In your yard:
• Don’t allow water to stand for more than two days.
• Check for standing water in birdbaths, pet dishes, buckets, cans, outdoor toys, wheelbarrows, old tires, boats and flowerpots.
• Remove any water that collects on pool covers.
• Clear leaves and twigs from eaves, troughs and gutters.
• Fill in low areas in lawns.
• Repair leaky pipes and outside faucets, as well as damaged window and door screens.
• Let neighbors know about potential mosquito breeding grounds on their property, or report stagnant water to the county at (602) 506-6616.
To reduce the chances of being bitten:
• Stay indoors from dusk to dawn, when mosquitoes are most active.
• Wear loose-fitting clothing, long sleeves and long pants.
• Apply insect repellent containing DEET to clothing as well as exposed skin.
• Do not use insect repellent on children under 2.
• For information or to report a mosquito problem or get free mosquito-eating fish, contact Maricopa County Vector Control, (602) 506-0700, or go to www.maricopa.gov/wnv
• You can also find information online at www.westnileaz.com or call a 24-hour hot line at (800) 314-9243 or (602) 364-4500.
— Tribune intern Thomas Keating contributed to this report.