Lyme Disease: Symptoms, Diagnosis, and Treatment
Also known as: Lyme borreliosis, Borreliosis
What Is Lyme Disease?
Lyme disease is a bacterial infection transmitted by the bite of a tick infected with Borrelia burgdorferi. CDC researchers estimate that about 476,000 people are diagnosed and treated for Lyme disease each year in the United States, based on insurance claims from 2010 to 2018. Cases are heavily concentrated: roughly 81% occur among residents of 14 high-incidence states in the Northeast, mid-Atlantic, and upper Midwest, with another 8% in adjoining states. Left untreated, the infection can spread beyond the site of the bite.
Symptoms
The most characteristic sign is erythema migrans, a rash that gradually spreads outward from the bite site and appears 3 to 30 days after the tick bite. It is often described as a “bull’s-eye,” though many rashes are uniformly red. Fever, headache, fatigue, and muscle and joint aches are common alongside it.
Doctors in the United States describe the infection in three stages:
- Early localized disease: the erythema migrans rash, often with flu-like symptoms
- Early disseminated disease: typically weeks after infection, as the bacteria spread. This can bring neurological symptoms (facial nerve palsy, meningitis) or cardiac problems such as conduction abnormalities, palpitations, chest pain, or shortness of breath
- Late disseminated disease: months after infection, most often Lyme arthritis affecting large joints, especially the knees, and sometimes cognitive problems or numbness and tingling
Diagnosis
Diagnosis relies first on the clinical exam. In a patient with possible tick exposure in an area where Lyme disease is common, an erythema migrans rash is enough on its own to start treatment, and guidelines recommend clinical diagnosis rather than waiting for lab confirmation.
Without that classic rash, doctors use antibody testing in a standard two-tiered protocol: an enzyme immunoassay (EIA) or indirect fluorescent antibody test, followed if positive or equivocal by IgM and IgG immunoblots (Western blot). Antibodies can take several weeks to develop, so testing too early can miss an infection.
Treatment
Treatment relies on antibiotics matched to the stage of disease:
- For the erythema migrans rash, a 10-day course of doxycycline, or a 14-day course of amoxicillin or cefuroxime axetil. Guidelines specifically recommend these over longer courses
- For people who cannot take those drugs, azithromycin is a second-line option, usually for 7 days in the United States
- Intravenous ceftriaxone for severe neurological involvement or for Lyme carditis serious enough to require hospitalization, switching to an oral antibiotic as the patient improves
- Lyme arthritis is treated with a 28-day oral course first, with IV ceftriaxone reserved for an inadequate response
- Clinical follow-up after treatment to confirm symptoms have resolved
Prevention
Prevention relies on avoiding tick bites: wear long sleeves, pants, and closed shoes in wooded or grassy areas, and use repellents such as DEET on skin and permethrin on clothing. Check your skin thoroughly after time outdoors.
Any tick you find should be removed promptly and mechanically with clean, fine-tipped tweezers, grasping it as close to the skin as possible. Transmission usually requires the tick to stay attached for many hours, so prompt removal matters.
After a high-risk bite (an Ixodes tick, in a highly endemic area, attached for 36 hours or longer), guidelines recommend a single 200 mg dose of oral doxycycline within 72 hours of removing the tick, or 4.4 mg/kg for children up to a 200 mg maximum. For bites that are low or equivocal risk, no preventive antibiotic is recommended, and for people who develop no symptoms after such a bite the guidance is observation rather than antibiotics.
Risk Factors
Risk rises with outdoor activities that increase tick exposure, such as gardening, hunting, and hiking, or walking through high grass in areas where Lyme disease occurs. Ticks are most abundant in or near wooded areas, and a pet that carries infected ticks home can bring the exposure to you. Timing matters as well: most tick bites happen in the warmer months, roughly April through September, when ticks are most active and people spend more time outdoors. So does where you live, since the large majority of U.S. cases are concentrated in the Northeast, mid-Atlantic, and upper Midwest.
When Should You See a Doctor?
Any spreading rash around a tick bite, or unusual symptoms (fever, joint pain, facial droop, palpitations, or neurological symptoms) in the weeks following exposure, should prompt a medical visit without delay. If you are unsure, see a doctor quickly rather than waiting to find out whether the rash fades.
Key takeaway: Lyme disease is effectively treated with antibiotics when caught early, which is why it’s important to watch any tick bite closely and see a doctor quickly if a spreading rash appears.
Sources
- Centers for Disease Control and Prevention (CDC), Emerging Infectious Diseases, estimating the frequency of Lyme disease diagnoses in the United States, 2010 to 2018
- MedlinePlus, U.S. National Library of Medicine Lyme disease information, including where blacklegged ticks are found and the April to September peak in tick bites
- MedlinePlus Medical Encyclopedia, Lyme disease stages and symptoms, and risk factors including gardening, hunting, hiking, walking in high grass, and pets carrying ticks home
- Infectious Diseases Society of America, American Academy of Neurology, and American College of Rheumatology, 2020 clinical practice guidelines for the prevention, diagnosis, and treatment of Lyme disease
- StatPearls, National Center for Biotechnology Information (NIH), Lyme disease clinical review