Four patients in August and one in July were diagnosed with relatively rare Vibrio vulnificus infections, according the state Department of Public Health.
Those infections lead to serious illness that could result in hospitalization or limb amputation, the department said.
"The identification of these five cases over two months is very concerning," said Dr. Matthew Cartter, the state epidemiologist for the Health Department. "This suggests the Vibrio bacteria may be present in salt or brackish water in or near Long Island Sound, and people should take precautions."
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Just seven such infections were reported in Connecticut between 2010 and 2019.
The cases reported this summer came in adults ages 49 and 85 years old from Fairfield, Middlesex and New Haven counties.
All of the cases involved people who had pre-existing wounds or sustained a wound and were then exposed to salt or brackish water while boating, swimming or crabbing the department said.
The Department urged anyone headed to the Sound to cover any wounds, recent piercings or new tattoos with waterproof bandages and wash them thoroughly with soap.
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