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

GREENWICH, CT — The Connecticut Mosquito Management Program on Tuesday announced that mosquitoes trapped in Mianus River Park in Cos Cob have tested positive for West Nile Virus (WNV).

These are the first positive mosquitoes identified by the Connecticut Agriculture Experiment Station (CAES) in Greenwich this year, the Greenwich Department of Health said in an announcement.

In addition to Greenwich, WNV-positive mosquito pools have been found in Bridgeport, Easton, Stamford and Wallingford.

The mosquitoes trapped are generally bird and mammal biting which breed in standing water often found in artificial containers like discarded tires, birdbaths and catch basins.

In 2024, nine Connecticut residents developed WNV-associated illness; the cases were not fatal. So far this year, Eastern Equine Encephalitis (EEE) has not been isolated in mosquitoes in Connecticut.

The State Mosquito Management Program will continue to trap and test mosquitoes at three testing sites in Greenwich as part of their program which will run through October, the Greenwich Department of Health said.

Greenwich will also continue the fight against WNV by conducting a preemptive larviciding program that includes the treatment of public and private roadway catch basins, public school ground catch basins and other property owned and operated by the town as needed.

This year’s program began in June, and 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," said Director of Health Caroline Calderone Baisley in a news release. "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 echoed Baisley's comments, and said residents "must be vigilant" in eliminating standing water on their properties and protecting themselves from biting mosquitoes.

"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. A mosquito 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 to 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 experience serious illness that affects the central nervous system.

In a minority of infected persons, especially those over 50 years old, WNV can cause serious illness, including encephalitis and meningitis, according to the Greenwich Department of Health.

Infection can lead to death in three to 15 percent of persons with severe forms of the illness.

"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 added.

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 on the label (10 percent or less DEET for children and no more than 30 percent DEET for adults). Always wash treated skin when returning indoors.
• Avoid application of repellents with DEET on infants and small children.
• Cover arms and legs of children playing outdoors.
• Cover playpens or carriages with mosquito netting.
• Don’t camp overnight near stagnant or standing water.

Eliminate standing water by:

• Getting rid of any water holding containers (old tires, etc.).
• Rake out puddles and drain ditches, culverts, gutters, pool and boat covers.
• Cover trash containers.
• Chlorinate your backyard pool and empty wading pools when not in use.
• Change the water in birdbaths daily.
• Keep grass cut short and shrubbery well trimmed around the house so adult mosquitoes cannot hide there.
• Ponds and stagnant water bodies that do not support fish, frogs or other amphibians that eat mosquito larvae may be treated with a biological control agent such as Bacillus Thuringiensis Israelensis (BTI). It is suggested that the Department of Health or Conservation be contacted when treatment is considered.

For more information, visit the health department page on the town website.