Mosquitoes Test Positive For West Nile Virus In Greenwich: Health Department

GREENWICH, CT — Mosquitoes trapped in Mianus River Park on the Stamford line in the Old Greenwich area have tested positive for West Nile Virus, according to an announcement from the Greenwich Department of Health, which cited the State of Connecticut Mosquito Management Program.

These are the first positive mosquitoes identified by the Connecticut Agricultural Experiment Station (CAES) in Greenwich this year. Additionally, WNV-positive mosquitoes have been found in 10 other CT towns.

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The Greenwich Department of Health noted that the trapped mosquitoes - Culex pipiens - are generally bird and mammal-biting mosquitoes that breed in standing water often found in artificial containers like discarded tires, birdbaths and catch basins.

In 2025, six CT residents were hospitalized with WNV disease, including one death in Fairfield County, according to the health department. So far this year, Eastern Equine Encephalitis (EEE) has not been isolated in mosquitoes in CT.

The State Mosquito Management Program continues to trap and test mosquitoes at three testing sites in Greenwich as part of its program and will continue through October.

Greenwich continues to conduct a preemptive larviciding program, which includes the treatment of public and private roadway catch basins, public school ground catch basins and other properties owned and operated by the town, the health department said. This year's program began in June; larvicide is reapplied every four to six weeks.

"Controlling the mosquito population in the larval stage through the application of larvicide has been found to be a prudent action; however, this measure only helps to reduce the mosquito population, not eliminate it," Greenwich Health Director Caroline Calderone Baisley said in an announcement.

"The recent warm weather and periodic rain events have increased the ability for mosquitoes to breed. Residents are encouraged to protect themselves whenever they are outdoors."

Greenwich Director of Environmental Services Michael Long noted that although the town's larvicide program treats catch basins, the general public must be vigilant and eliminate standing water on their own properties and protect themselves from mosquitoes at all times.

"It is important to recognize that the highest risk of exposure to West Nile virus-infected mosquitoes is during the months of August and September," Long said.

WNV is spread to humans by the bite of an infected mosquito, which becomes infected when it bites a bird carrying the virus. WNV is not spread by person-to-person contact or directly from birds to people.

General symptoms occur suddenly between five and 15 days following the bite of an infected mosquito and range from slight fever, headache, rash, swollen lymph nodes, nausea, malaise and eye pain, to the rapid onset of severe headache, high fever, stiff neck, disorientation, severe muscle weakness, gastrointestinal symptoms, coma or death, the Greenwich Department of Health said.

Most people who are bitten by an infected mosquito are able to fight off infection and experience mild or no symptoms at all.

Some individuals, including the elderly and persons with compromised immune systems, can develop serious illness affecting the central nervous system.

In a minority of infected persons, especially those over age 50, WNV can cause encephalitis and meningitis. Infection can lead to death in 3 percent to 15 percent of people with severe forms of the illness, according to health department officials.

"The finding of WNV-positive mosquitoes in Greenwich marks the time to emphasize that personal protection measures are extremely important against biting mosquitoes during the day and at night," Baisley said.

The following precautions should be taken when outdoors:

• Avoid outdoor activities at dawn and dusk when mosquitoes are most active.
• Wear long-sleeved shirts and long pants.
• Use mosquito repellent according to the manufacturer's directions (10 percent or less DEET for children and no more than 30 percent DEET for adults). Wash treated skin after returning indoors.
• Avoid applying DEET repellents to infants and small children.
• Cover children's arms and legs when they are playing outdoors.
• Cover playpens or strollers with mosquito netting.
• Don't camp overnight near stagnant or standing water.

Eliminate standing water by:

• Getting rid of water-holding containers (old tires, etc.).
• Raking out puddles and draining ditches, culverts, gutters, pool and boat covers.
• Covering trash containers.
• Chlorinating backyard pools and emptying wading pools when not in use.
• Changing the water in birdbaths daily.
• Keeping grass cut short and shrubbery well trimmed around the house so adult mosquitoes cannot hide there.
• Treating ponds and stagnant water bodies that do not support fish, frogs or other amphibians with a biological control agent such as Bacillus thuringiensis israelensis (BTI), after consulting the Department of Health or Conservation.

The Town of Greenwich Mosquito Management Brochure is available throughout the community and on the town's website.

More information on mosquitoes in CT can be found here.