Wilton has become the 21st town in Connecticut where a mosquito has tested positive for West Nile virus.

The mosquito was trapped Sept. 9, along Saunders Drive. It was of the species Culex restuans, the same type of mosquito that tested positive in Wilton for West Nile last year. A total of seven mosquitoes were tested Sept. 9 at the trap. Test results were not available for the Spectacle Road trap.

This information was released today, Sept. 20, by the State Mosquito Management Program. Since June 27, the Connecticut Agricultural Experiment Station (CAES) has identified West Nile virus-positive mosquitoes at trap sites in 20 other towns: Branford, Bridgeport, Darien, East Haven, Fairfield, Glastonbury, Greenwich, Groton, Manchester, New Haven, Norwalk, Plainfield, Stafford, Stamford, Stratford, Voluntown, Wallingford, Waterford, West Haven and Westport.

Two Connecticut residents have been diagnosed with West Nile virus-associated illnesses including a Stratford resident, 60-69 years with onset of illness during the last week of July, and a Stamford resident, 80-89 years with onset during the third week of August. Both are recovering.

“Although mosquito populations are declining, we continue to find mosquitoes infected with West Nile and eastern equine encephalitis viruses in several areas of the state,” said Dr. Theodore G. Andreadis, chief medical entomologist with the CAES. “It is important that people continue to take precautions to avoid mosquito bites.”

When the West Nile virus-positive mosquito was caught at the trap on Saunders Drive on July 16, 2012, Dr. Andreadis said it was unusual to find positive mosquitoes in towns like Wilton. In this part of the state they are more common in towns south of the Merritt Parkway.

He identified Culex restuans as “an efficient vector.” It predominates in rural locations, but is also found in wooded areas, artificial containers and more natural sites as opposed to catch basins and storm drains.

West Nile virus activity varies each year, according to the CAES, and is difficult to predict. Generally, the greatest risk for transmission to people from infected mosquitoes is from early August to mid-September.

Mosquitoes with the eastern equine encephalitis virus have been identified in four towns: Haddam, Hampton, Plainfield and Voluntown. A horse stabled in Griswold died from an illness associated with the virus during the second week of September. No human infections have been identified.

Precautions to take include minimizing time outdoors between dusk and dawn, and wearing shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time. Also, the use of mosquito repellent can be effective.

Information: ct.gov/mosquito.