A dead bird that tested positive for West Nile virus has been found in Petaluma, the Marin/Sonoma Mosquito and Vector Control District District said Thursday.

The dead bird, an American crow, is the first infected bird found this year in the two counties and was found near Magnolia Avenue and Keokuk Street, said Nizza Sequeira, a spokeswoman for the Marin/Sonoma Mosquito and Vector Control District. West Nile virus is increasing throughout California, especially in areas where temperatures are high.

Mosquito abatement crews are currently patrolling neighborhoods in the Larkspur and Corte Madera areas. Standing water, coupled with spikes in temperature create an ideal situation for rapid mosquito production and elevated levels of the virus within the mosquito, which makes transmission to humans, birds and animals more likely, Sequeira said.

"The mild weather has been in our favor this year, but should we see a sharp increase in temperatures for an extended period of time, we will likely begin to see more West Nile virus activity in the area," Sequeira said. Increased surveillance efforts are already underway in the vicinity of the area where the dead bird was found and adult mosquito surveillance traps have been set to assess whether they are carrying the virus.

All known mosquito breeding sources are being monitored and technicians are scouring the area in search of other areas that may be producing mosquitoes.

The district is asking resident to eliminate standing water in rain barrels, old tires, buckets and kiddie pools and report neglected swimming pools, or any area other areas that could be producing mosquitoes.

Foreclosed homes with neglected swimming pools are also a concern since they can produce over 1 million mosquitoes each. "The bottom line is that it if something looks like it could produce mosquitoes, it probably is, and should be reported to the district," Sequeira said.