A group of mosquitoes has tested positive for West Nile virus for the first time in Connecticut this year, state environmental officials said Friday.

The mosquitos, which were trapped in Stratford on July 22, were a predominantly bird-biting species, the Department of Environmental Protection said.

John Anderson, director of the Connecticut Agricultural Experiment Station, said fewer mosquitoes were collected this year than in 2001.

Still, "the threat of West Nile virus remains relatively strong this year," he said.

As of July 31, 11 crows in Bristol, Fairfield, New Haven, North Branford, North Haven, Rocky Hill, Stratford, Waterbury and West Hartford have tested positive for the virus.

Joxel Garcia, commissioner of the state Department of Public Health, said the risk of West Nile virus infection begins to increase in midsummer. Residents should take steps, such as eliminating standing water, to reduce the risk of mosquitos near their homes.