A deer tick, the species which carries Lyme disease, makes its...

A deer tick, the species which carries Lyme disease, makes its way around a petri dish at a Stony Brook University lab last month. Credit: Newsday/John Paraskevas

Brain fog. Fatigue. Body aches.

These are some of the symptoms people with Lyme disease have reported even months after being treated for the tick-borne illness — a condition called Post-Treatment Lyme Disease Syndrome.

Also referred to as chronic Lyme, researchers at Stony Brook Medicine recently launched a study to try and figure out why some people recover relatively quickly from the disease while others struggle for months or even years. The work is especially critical for Long Island, a hot spot for Lyme and other tick-borne diseases, and could help answer questions surrounding long COVID-19 and other chronic conditions.

Dr. Luis Marcos, an infectious disease expert who is heading the study, said he and his colleagues have heard from many patients complaining about symptoms months after they were diagnosed with Lyme disease.


  • Researchers at Stony Brook Medicine have started a study to help determine why some people who get Lyme disease have symptoms for months and sometimes years.
  • Experts estimate 20% to 30% of people treated for Lyme disease may develop the condition called Post-Treatment Lyme Disease Syndrome.
  • Researchers hope to enroll 50 to 60 Long Islanders for the study.

“They ask if we know anything about a treatment,” said Marcos, who said 20% to 30% of people treated for Lyme disease may develop the condition. “We as doctors feel frustrated that we don’t have the answer.”

Dr. Luis Marcos, associate professor of medicine at Stony Brook...

Dr. Luis Marcos, associate professor of medicine at Stony Brook University, inspects deer tick specimens at the infectious disease lab. Credit: Newsday/John Paraskevas

Infectious disease experts have been grappling to understand the origins of Post-Treatment Lyme Disease Syndrome. Some have compared it to the nascent research into long-term COVID-19 and believe studying the two syndromes can help shed light on both of them.

The study Marcos is heading at Stony Brook Medicine will focus on patients newly diagnosed with Lyme disease as well as patients diagnosed with both Lyme and babesia, a parasite carried by ticks that infects red blood cells and causes the disease babesiosis.

It was funded with approximately $750,000 from the Congressionally Directed Medical Research Programs in the U.S. Department of Defense. Marcos and Stony Brook, which is collaborating with New York Medical College on the project, were one of four researchers across the nation to receive the grant as part of the CDMRP’s Tick-Borne Disease Research Program.

Marcos said they are hoping to enroll 50 to 60 people on Long Island for the three-year study.

Researchers will evaluate their blood after they are enrolled and then at one- and six-month intervals. If participants have a rash — a sign of a tick bite — a small portion of skin will be biopsied for review.

“People have tried antibiotics, but some are not effective treatments, which means the bacteria is no longer the problem, but rather something in the immune system,” Marcos said.

Samples from patients who have symptoms six months after treatment will be compared with samples from patients who no longer have symptoms at the six-month mark.

“We want to compare the immune response to know the root of the problem in the immune system,” he said.

Lyme disease is caused by the bacterium Borrelia burgdorferi, transmitted to humans via bites from infected blacklegged ticks, according to the Centers for Disease Control and Prevention. While the initial illness includes fevers, headaches and rashes, untreated Lyme disease can spread to a person’s joints, heart and nervous system.

The CDC said there is no way of knowing how many people in the U.S. get Lyme disease, but note about 30,000 cases are reported from state health departments every year. The agency says other estimates suggest about 476,000 people may get Lyme disease annually.

Dr. John Aucott, director of the Johns Hopkins Lyme Disease Clinical Research Center and an expert in the study of chronic Lyme, said it is vital to study the disease because the number of people infected with tick-borne diseases is growing, both in cases and geographic regions.

“If there are half a million new cases every year, which is the estimate, maybe 10% or more go on to develop Post-Treatment Lyme Disease Syndrome. That’s 50,000 new cases of a chronic illness every year," he said. "Sometimes they get better, but a lot of times they don’t because we don’t know exactly how to intervene effectively.”

Aucott’s research in 2022 helped establish that Post-Treatment Lyme Disease Syndrome is an actual condition caused by Lyme disease and not other illnesses or health factors. That study also showed 14% of the people treated for early Lyme disease went on to develop Post-Treatment Lyme Disease Syndrome. 

Some theorize it can be triggered by an inflammatory response by the remnants of the infection or its impact on the nervous system.

“But until we know that and have ways to measure those things, we won't know what the right treatment is,” Aucott said.

Aucott said because the symptoms of Long COVID-19, Chronic Fatigue Syndrome and Post-Treatment Lyme overlap, research into each of those illnesses may be able to help all of them.

“We are already finding common links,” he said. “Since they share a similar appearance clinically, maybe they share some underlying mechanisms.”

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