Three young adults died suddenly in the past year of severe heart inflammation induced by Lyme disease, a cardiac manifestation that has surprised some medical investigators.

One of those deaths occurred in New York, but not on Long Island, say federal scientists at the Centers for Disease Control and Prevention, who emphasized Thursday that sudden cardiac death is possible in young people infected by Lyme bacteria.

Before these three Lyme-related sudden deaths, only four cases had been reported in medical history. Lyme disease was first discovered and described in 1976.

Writing in Thursday's issue of the CDC's Morbidity and Mortality Weekly Report, a team of the agency's researchers noted their investigation began after the death of a young man whose car had careened off a road.

Inexplicably, his heart had stopped.

Equally puzzling was the unusual tissue pattern doctors found in his heart muscle upon autopsy. The man had suffered from carditis, an inflammation of the heart muscle.

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Further investigation revealed an invasion of his heart by the Lyme bacterium, the source of the severe cardiac inflammation. As the team continued looking into Lyme-related carditis, it found two other young people, identified only as being between the ages of 26 and 38, having also died of sudden cardiac arrest. The deaths occurred between November 2012 and July 2013.

Dr. Jorge Benach, a Lyme disease expert at Stony Brook School of Medicine, said the sudden deaths of people so young, especially without underlying cardiac problems, is highly unusual. Yet, Lyme-related carditis is not an anomaly, he said.

"We have known about [Lyme-related] carditis since the beginning," said Benach, a professor of molecular genetics and microbiology.

"About 8 to 10 percent of Lyme cases have carditis," Benach said.

Nevertheless, sudden cardiac arrests have occurred among people who were infected by both the Lyme bacterium and the parasite that causes babesiosis, a malaria-like illness, which, like Lyme, is transmitted by ticks.

Although worrisome, the three sudden cardiac deaths do not suggest recent genetic mutations in the Lyme bacterium that make it more virulent, Benach said.

CDC scientists Thursday said doctors and patients should be aware of Lyme carditis, which can cause heart palpitations, chest pain, lightheadedness, fainting and shortness of breath. These symptoms occur in addition to the commonly recognized manifestations of Lyme disease, such as fever, rash and body aches.

Lyme disease is normally transmitted in summer when ticks are most active, experts say.

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Though Lyme-related carditis is relatively rare, Benach said, his laboratory research shows that Lyme bacteria have an affinity for the heart.

"When we infect mice with the Lyme disease organism, it preferentially goes to the heart," Benach said. "Carditis is an invasion of the heart muscle by the organism and following this invasion, inflammatory cells move into the heart tissue."

CDC researchers, meanwhile, found that all three victims of sudden cardiac arrest lived in high-incidence Lyme disease regions of the Northeast where Lyme has been on the rise in recent years. Long Island is part of an active Lyme disease belt, which stretches throughout the Eastern Seaboard.