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- Posted September 22, 2025
Lyme Disease: What To Know About Symptoms, Treatment & Prevention
Lyme disease is the most common vector-borne illness in the United States, a potentially disabling infection caused by bacteria transmitted through the bite of an infected tick to people and pets.
Another possible route of transmission, which is less well known and understudied, is from an infected pregnant mother to her unborn baby.
Each year, the U.S. sees about 500,000 new cases of Lyme disease, according to statistics released in 2018 by the U.S. Centers for Disease Control and Prevention (CDC).
While awareness has grown, Lyme disease is often misunderstood, misdiagnosed or treated late, sometimes leading to prolonged illness. As a result, more than 2 million suffer from its debilitating later stage symptoms.
Here’s what to know about how Lyme disease spreads, symptoms to watch for, treatment options and how to live well even if symptoms persist.
What Is Lyme disease?
Lyme disease is an infection caused mainly by the bacterium Borrelia burgdorferi in the United States. The bacteria are transmitted to humans through the bite of infected blacklegged ticks: the Western blacklegged tick (Ixodes pacificus) and Eastern blacklegged tick (Ixodes scapularis), sometimes called a deer tick.
The disease was first recognized in the 1970s after an outbreak in Lyme, Connecticut. Today, Lyme has been reported in all 50 states. However, while the geographic areas inhabited by ticks that carry Lyme-causing bacteria have expanded, ticks carrying these bacteria have not been identified in every state at this time.
The highest rates are in the Northeast, Upper Midwest, and parts of Northern California and the Pacific Northwest.
How Is Lyme disease transmitted?
Ticks pick up the Lyme bacteria by feeding on infected animals, such as mice or birds. When an infected tick bites a person, the bacteria can be transmitted through the tick’s saliva.
Ticks go through three life stages: larva, nymph and adult. Nymphs, which are roughly the size of a poppy seed, cause most human infections because they are easy to miss and active in warmer months when people are more often outdoors.
How long a tick must be attached to a person’s skin before it transmits disease can vary. One European study documented six cases of confirmed Lyme disease in which tick attachment lasted less than six hours and nine more where transmission occurred in less than 24 hours.
While it can take 24 to 36 hours for the bacteria to travel from the tick’s midgut to its salivary glands, transmission can start immediately in an estimated 10% of infected ticks that already carry bacteria in their saliva (due to having taken a partial blood meal before detaching and reattaching to a new host).
Removing ticks promptly, ideally before they attach, is thus one of the best ways to prevent infection.
What are the symptoms of Lyme disease?
Symptoms can vary from mild to severe and may appear days, weeks or even months after the tick bite. Not everyone notices a tick or remembers being bitten.
Symptoms vary from person to person and can be intermittent or changing and overlap across different stages, which makes diagnosis more confusing. Potential symptoms include but are not limited to:
Early localized disease (days to weeks after infection):
Expanding rash, sometimes with a bull’s-eye appearance (erythema migrans) — Importantly, a classic bullseye appearance with central clearing of the rash occurs in a minority of U.S. patients (about 20% reported in one study), although up to 80% of patients may have a rash of varying shapes
Fatigue
Fever and chills
Headache
Muscle and joint aches
Swollen lymph nodes
Early disseminated disease (weeks to months after infection):
Multiple rashes on the body
Facial weakness or paralysis, usually on one side but can be both (Bell’s palsy)
Severe headaches and neck stiffness
Pain, tingling or numbness in the arms or legs
Cardiac problems, most commonly conduction disturbances (“heart block”) but also a variety of rhythm disturbances, pericarditis or myocarditis
Late disease (months to years after infection):
Joint swelling or pain, typically in a single or a few large joints such as the knee
Neurological problems, such as numbness, tingling, vision/hearing problems or cognitive/memory issues.
Reported across all stages of disease:
Neuropsychiatric or behavioral manifestations (mood swings, anxiety, depression)
Presumed dysautonomia symptoms, such as dizziness, lightheadedness, increased heart rate when standing, and temperature regulation issues, have also been described.
An estimated 10 to 20% of patients treated for Lyme disease with a recommended two- to four- week course of antibiotics will have lingering symptoms, which commonly include fatigue, joint/muscle/nerve pain and cognitive impairment (such as “brain fog” or problems concentrating). In some cases, Lyme carditis and progressive neurologic Lyme have proven fatal.
Some people never develop the classic rash or other early symptoms, or these signs go unrecognized, so they first present with early disseminated or late-stage symptoms.
Why is Lyme disease sometimes missed?
Lyme disease is sometimes called “the great imitator” because its symptoms resemble those of other conditions such as flu, chronic fatigue syndrome or autoimmune disorders. Diagnosis is based on a combination of symptoms, possible tick exposure and lab tests.
The standard blood tests detect antibodies to Lyme bacteria and not the infection itself. Therefore, these tests may not show a positive result in people with early infection, as their bodies have not yet produced enough antibodies.
It has long been known that the diagnostic test recommended by the CDC for Lyme disease misses up to 60% of early-stage cases.
Importantly, it can also fail to detect later-stage disease, contributing to many missed diagnoses. For this reason, doctors rely on symptoms and exposure history in addition to lab tests when making a clinical diagnosis.
How can you prevent Lyme disease?
The best way to avoid Lyme disease is to prevent tick bites. Here’s how:
Use U.S. Environmental Protection Agency-registered insect repellents containing DEET, picaridin or IR3535.
Treat clothing and gear with permethrin.
Wear long sleeves, long pants and closed shoes when in grassy or wooded areas.
Tuck pants into socks to block ticks from crawling up legs.
Stay in the center of trails and avoid tall grass or leaf litter.
Check your body, clothing, gear and pets for ticks after outdoor activities.
Shower within two hours of coming indoors to help remove ticks before they attach.
If you find an attached tick, remove it promptly with fine-tipped tweezers, grasping it close to the skin and pulling straight out.
Once removed, consider sending the tick for testing to determine what pathogens it may be carrying. This will give you a good gauge of what to look out for.
Of note, if the tick is carrying pathogens, it does not necessarily mean they were passed to you, and if the tick is not carrying pathogens, you should still consider that it is possible you were bitten by another tick that went unnoticed.
How Is Lyme disease treated?
Early Lyme disease is typically treated with oral antibiotics, such as doxycycline, amoxicillin or cefuroxime. The Infectious Diseases Society of America (IDSA) and CDC recommend 10 to 14 days of antibiotics for early-stage Lyme disease with the caveat that regimens “may need to be adjusted depending on factors such as age, medical history, underlying health conditions, pregnancy status or allergies.”
The International Lyme and Associated Diseases Society (ILADS), recommends four to six weeks of antibiotics, with the duration tailored to the patient’s response and clinical circumstances; ILADS guidelines also state that, when necessary, antibiotic therapy should be extended. Patients with certain neurological or cardiac forms of illness may require intravenous treatment with drugs such as ceftriaxone or penicillin.
More advanced neurological or joint disease sometimes requires treatment with longer and more complex regimens or IV antibiotics. Many people can recover fully with prompt treatment, but some continue to experience symptoms for months or years after finishing antibiotics.
What about lingering symptoms?
Persistent symptoms after treatment, sometimes called persistent Lyme disease (PLD) or Post Treatment Lyme Disease Syndrome (PTLDS), can include, but are not limited to, fatigue, pain and cognitive difficulties. The cause is debated. The possibility of unidentified coinfections contributing to lingering symptoms should be excluded with testing.
Additional hypotheses for the cause of persistent symptoms include incompletely eradicated Lyme bacteria, lingering immune responses (autoimmunity), residual tissue damage and other complicating factors acting individually or in combination.
Scientific studies funded by Bay Area Lyme Foundation have shown that Lyme infection can persist post-treatment due to Lyme bacteria that are not completely eradicated.
On the horizon: Next steps in research
Researchers across the country, including teams supported by Bay Area Lyme Foundation and its affiliates, are working to close critical gaps in Lyme disease prevention, diagnosis and treatment.
Current priorities include creating more sensitive and specific diagnostic tests that not only better detect infection early on but also improve recognition of past and late-stage disease, distinguish active from past infections, and confirm when treatment has been successful.
Efforts are also underway to identify new therapeutic options for patients with persistent symptoms, to explore vaccines, develop novel prevention tools, and to deepen scientific understanding of Lyme bacteria and the immune system’s response to it.
How Bay Area Lyme Foundation is powering progress
Bay Area Lyme Foundation funds innovative research and fosters collaboration among scientists, clinicians and public health experts to accelerate solutions for Lyme disease.
The Foundation’s initiatives include supporting the development of next-generation diagnostics and advancing potential new treatments. It is the founding/operating Lyme Disease Biobank, a vital resource of well-characterized biological samples — including donated blood, urine and tissue — for researchers worldwide.
With its mission to make Lyme disease easy to diagnose and simple to cure, Bay Area Lyme Foundation is committed to reducing the impact of Lyme and other tick-borne diseases for patients everywhere.
The bottom line
Lyme disease is common, but with awareness, early diagnosis and effective treatment, most people recover fully.
To reduce the burden of the disease and help those with persistent symptoms, continued research into new, more accurate diagnostics and improved treatments is essential.
Prevention is key: Protect yourself against tick bites, check for ticks after being outdoors, and seek medical care promptly if you develop symptoms.
About the expert
Charlotte Mao, MD, MPH, Bay Area Lyme Foundation, is a pediatric infectious diseases physician whose area of clinical focus is Lyme disease and associated infections. She is a member of Bay Area Lyme Foundation’s Advisory Board and Science Committee. Graduating from Harvard Medical School, she completed her pediatric residency and pediatric ID fellowship at Boston Children’s Hospital. Her prior area of subspecialty during 25 years at Boston Children’s Hospital was pediatric HIV clinical care and clinical research. She turned her focus to Lyme disease and associated infections on gaining extensive clinical experience with pediatric Lyme disease in the referral infectious disease clinic there. Later joining the Department of Pediatric Infectious Disease at Massachusetts General Hospital, she provided consultative pediatric infectious disease specialty care in a multidisciplinary clinic for children with complex Lyme disease and associated infections at the Dean Center for Tickborne Illness at Spaulding Rehabilitation Hospital. Click here to read her published paper entitled Microbes and Mental Illness: Past, Present, and Future.
