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Extreme summer heat and rain is creating a perfect storm for Connecticut's mosquitoes

A Connecticut Agricultural Experiment Station map tracks Connecticut's West Nile virus cases as of September 05, 2023.
A Connecticut Agricultural Experiment Station map tracks Connecticut's West Nile virus cases as of September 05, 2023.

The Connecticut Agricultural Experiment Station (CAES) is continuing to report more positive cases of West Nile virus among mosquitoes in the state. Experts say the excessive warm, damp conditions this summer are helping the insects thrive.

Mosquitoes proliferate when there are high temperatures, humidity and standing water. This summer, the state saw that a lot – with record-breaking heat and rain in July.

Over 280,000 mosquitoes have been trapped and tested so far this year in Connecticut, according to data released in early September. That’s a major increase from the amount normally expected this time of year, according to Dr. Philip Armstrong, program director of the Connecticut Mosquito Monitoring Program.

“We were on track for a normal year, and then with all that heavy rainfall, the numbers really surged in the late season,” Armstrong said.

The insects may become more abundant into the fall, he said, but mosquito “season” in Connecticut typically ends by the first hard frost, usually around October. But as climate change drives summers to be warmer and longer, that could change.

Hotter summers can also create a higher risk of West Nile virus transmission, Armstrong said. So far this year, only one Connecticut resident has contracted West Nile virus and has since recovered, according to state health officials.

But this week’s data shows over 100 mosquitoes at the trapping stations have tested positive for West Nile virus this year, which is up from about 70 the previous week. The majority of the infected mosquitoes were trapped in Glastonbury, Wethersfield, Norwalk, Darien and Stamford.

Overall collection numbers tend to fluctuate year to year, depending on the weather. The data helps the state and towns decide where to focus mitigation efforts, Armstrong said.

“It gives us advance warning of the risk to humans,” Armstrong said. “You can track the virus amplification and there's usually a period of virus build up before humans get exposed.”

On Sept. 1, the state also reported that mosquitoes in Thompson, Connecticut, tested positive for eastern equine encephalitis (EEE), a very rare but severe illness that can infect humans. The last major outbreak of EEE was in 2019, with 19 cases across New England.

While there’s no “magic bullet” approach to reducing mosquitoes, Armstrong said, residents should still take steps to prevent getting bites, from removing standing water in and around the home, to wearing long clothing and insect repellent when outdoors for a while.

More information on preventing mosquito bites is on the Centers for Disease Control and Prevention’s website.

As Connecticut Public's state government reporter, Michayla focuses on how policy decisions directly impact the state’s communities and livelihoods. She has been with Connecticut Public since February 2022, and before that was a producer and host for audio news outlets around New York state. When not on deadline, Michayla is probably outside with her rescue dog, Elphie. Thoughts? Jokes? Tips? Email msavitt@ctpublic.org.