The Vector Control District places about 30 traps weekly, year round, to identify mosquitoes carrying viruses and isolate their breeding areas. The traps are randomly placed around residential areas and wetlands

Beginning Monday, as many as 70 traps will be set in the hope of quickly pinpointing the virus' arrival and eradicating the infected mosquitoes, said James Webb, the district's technical director.

Vector control employees will place traps in backyards, Webb said. The slender 4-inch tubes are attached to a canister of dry ice that emits carbon dioxide to mimick the breath of a warm-blooded animal. When the mosquito approaches the trap, a fan pulls it into the tube. The traps are collected after 24 hours and examined.