HARTFORD, Conn. (CBSNewYork) – Health officials in Connecticut are warning residents across the state about a mosquito-borne virus that can cause potentially fatal brain infections and has no treatment.

The Connecticut Department of Public Health says mosquitoes in 12 towns have already tested positive for Eastern Equine Encephalitis virus.

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EEE is rare and serious illness transmitted to humans by a mosquito bite and has already killed at least three people in the U.S. this year – including one case in New Jersey.

“Most people infected with EEE virus do not become ill. When symptoms do occur they can range from mild fever and headache to coma. Other symptoms include high fever, fatigue, muscle aches, neck stiffness, tremors, or confusion,” Connecticut health officials said.

“Severe cases include inflammation of the brain (encephalitis) which can lead to coma, convulsions, and death.”

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Making matter worse for residents in the Northeast, the CDC reports that there is no antiviral vaccine for EEE and patients who believe they’ve been infected should get to a doctor as soon as possible.

“The illness lasts one to two weeks, and recovery is complete when there is no central nervous system involvement,” the CDC explains.

The CDC added that one third of the patients who contract the rare illness die from it.

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To this point, there not been any human cases of EEE in Connecticut. Officials are urging residents to wear long-sleeved clothes when outside after dark and use insect repellent.