Chronic Lyme disease is caused by an infected tick bite that introduces bacteria into the bloodstream.
  • Chronic Lyme disease, or post-treatment Lyme disease syndrome, occurs when symptoms of Lyme disease persist for at least six months after treatment. 
  • Symptoms of post-treatment Lyme disease syndrome include impaired memory and disrupted sleep. 
  • Here's how to get a diagnosis and seek proper treatment for post-treatment Lyme disease syndrome. 
  • This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine. 
  • Visit Business Insider's homepage for more stories.

Lyme disease is the most common vector-borne illness, which are diseases spread by blood-feeding arthropods like mosquitos, fleas, or ticks in the US. It can typically be resolved with a brief round of antibiotics. But, for some people symptoms may stick around long after treatment and interfere with daily activities. Here's what you need to know about post-treatment Lyme disease syndrome, sometimes referred to as chronic Lyme disease.

What is chronic Lyme disease, or post-treatment Lyme disease syndrome? 

Chronic Lyme disease is an umbrella term that includes undiagnosed Lyme cases, as well as individuals with post-treatment Lyme disease syndrome (PTLDS). PTLDS occurs when symptoms of Lyme disease persist for at least six months after treatment. 

It's difficult to say how long symptoms of PTLDS linger because some people may never recover, says Elizabeth Maloney, MD, a Minnesota family practice physician and president of the Partnership for Tick-Borne Diseases. Recent studies haveshownthat people may experience symptoms several years after treatment. 

In recent decades, scientists and doctors have hotly debated the legitimacy of chronic Lyme disease due to uncertainty over what's causing the symptoms — a lingering infection or an overactive immune response — often leaving patients feeling frustrated and neglected. Therefore, most physicians prefer PTLDS to describe lingering Lyme symptoms, rather than the vague and controversial phrase "chronic Lyme."

What are the symptoms of post-treatment Lyme disease syndrome? 

PTLDS causes a broad range of symptoms that manifest throughout the body. Symptoms may vary depending on if someone has already received treatment. 

What causes Lyme disease?   

Lyme disease is caused by an infected tick bite that introduces the Lyme disease bacteria into the bloodstream. Ticks can bite any part of the human body, but commonly go for hidden areas like the scalp, armpits, and groin. 

Ticks must usually be attached for at least 36 hours to transmit Lyme disease. Then, the bacterium quickly leaves the bloodstream and moves into tissues, sometimes triggering symptoms like heart problems and arthritis.

Learn more about how to spot and treat a tick bite.

Can someone who's been treated for Lyme disease still have Post-Treatment Lyme Disease Syndrome? 

Physicians usually prescribe Lyme patients with a two to four week course of oral antibiotics. This resolves the majority of cases, says Eugene Shapiro, MD, a professor of pediatrics and epidemiology at Yale University. However, PTLDS could manifest when antibiotics fail to clear an infection and its related symptoms.

Because traces of the bacteria rapidly disappear from an individual's blood, testing for residual post-treatment infection is challenging, says Monica Embers, PhD, director of vector-borne disease research  at Tulane University's National Primate Research Center.

When patients face possible post-treatment complications, tests can't indicate whether these symptoms are driven by Lyme — versus something else entirely. According to Embers, current antibody tests are only about 50% to 60% accurate, but they grow more sensitive four or more weeks after the initial infection as people further develop antibodies.  

"What's desperately needed is a diagnostic test that can be used in chronic patients to demonstrate that they have had Lyme disease or continue to have a persistent infection, and we don't have that right now," says Embers. 

What causes post-treatment Lyme disease syndrome? 

There are a few different theories as to why some Lyme disease patients experience persisting symptoms, while others do not. These include:  

  • Effects on immune system and tissues: Lyme disease might impair the immune system, Maloney says. In trying to fight off the infection, the immune system may attack itself and worsen inflammation, possibly causing arthritis. More broadly, Lyme can cause complications like memory loss and numbness as the bacteria continues to spread. 
  • Persistent bacterial infection: PTLDS may occur if initial antibiotic treatment fails to clear the infection. But, until researchers find a way to detect lingering bacteria within the human body, there's no way to be sure whether Lyme stuck around.
  • Not Lyme disease-related: It's always possible that symptoms like fatigue and joint pain have completely unrelated causes, Shapiro says, particularly because some of these manifestations are not highly specific. But studies have begun to pinpoint a distinct set of PTLDS symptoms that might rule out other issues.

How common is post-treatment Lyme disease syndrome? 

Even after receiving the standard Lyme disease antibiotic treatment, about 10% to 20% of patients experience persisting symptoms. In 2016, there were up to 1.5 million PTLDS cases in the US. 

Historically, US Lyme cases have been undercounted, says Embers. The Centers for Disease Control and Prevention (CDC) have traditionally reported annual cases — about 45,000 per year between 2005 and 2010 — based on physicians' data. 

A 2015 analysis of health insurance records published in Emerging Infectious Diseases estimated around 329,000 annual Lyme diagnoses over the same period. If the CDC is missing a significant number of Lyme cases, they're likely to overlook the prevalence of PTLDS.

Another factor that obscures PTLDS cases is misdiagnosis. Because the full spectrum of PTLDS symptoms still isn't fully understood, it is commonly mistaken with other conditions, says Maloney.

Symptoms of PTLDS like fatigue and brain fog are also associated with chronic fatigue syndrome and fibromyalgia, making it easy for doctors to misdiagnose.

"Those labels might be labels of convenience because patients and physicians want to know what's making someone sick," Maloney says. "Since there's so much controversy in Lyme disease, some of these people will … just call it fibromyalgia and deal with it that way."

How do you treat post-treatment Lyme disease?

Research has found that antibiotics are likely ineffective to treat PTLDS, particularly for extended periods of time. And long-term antibiotic use can prove harmful: These medications could eventually hinder gut function, elicit antibiotic resistance, or cause infections at the IV site, says Shapiro.

Studies have looked into existing drugs like Antabuse — an alcoholism treatment — as well as intravenous immunoglobulin therapy, which is typically used for immune system disorders. However, there's no clinically proven treatment for PTLDS.


Lyme disease may persist long after initial treatment, but current testing methods can't yet confirm whether chronic symptoms like fatigue, joint pain, and brain fog are connected to ongoing infections. To protect yourself from Lyme, take precautions like wearing repellant and performing body checks when in a high-risk area. If you suspect an infection, make an appointment with your doctor.

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