Diseases beginning with L
U.S.-focused summaries with current official guidance links. For a diagnosis, personal vaccine schedule, pregnancy advice, or urgent symptoms, speak with a qualified clinician.
Lyme Disease
No vaccine availableDisease
A bacterial infection transmitted by infected blacklegged ticks in parts of the United States.
Symptoms
Early illness may cause fever, fatigue, headache, muscle or joint aches, swollen lymph nodes, and an expanding erythema migrans rash. Later disease can affect the joints, facial nerves, heart rhythm, or nervous system.
Typical duration
Early symptoms often begin 3 to 30 days after a tick bite. Most people recover after recommended antibiotics, although some have symptoms that take longer to improve.
How serious is it?
Untreated infection can cause facial palsy, meningitis-like illness, Lyme carditis, or arthritis. Fainting, chest symptoms, severe headache, weakness, or facial droop needs prompt care.
Treatment & management
Most cases are treated with oral antibiotics such as doxycycline, amoxicillin, or cefuroxime; the drug and duration depend on age, pregnancy, symptoms, and complications. Some neurologic or cardiac cases need intravenous treatment.
Vaccine: who and when?
No Lyme disease vaccine is currently available for people in the United States. Human vaccine candidates remain under study.
Last reviewed against official U.S. sources: September 5, 2026. This page provides general education, not medical advice.
More conditions in this letter
Explore additional source-led condition guides published in this A-Z library.
- Lactose IntoleranceLearn how lactose intolerance differs from milk allergy, how it is evaluated, and how to reduce symptoms while protecting calcium and vitamin D intake.
- Legionnaires’ DiseaseLearn how Legionnaires' disease spreads, which symptoms need urgent care, how clinicians test and treat it, and how water systems are managed.
- Lung CancerLearn which lung symptoms need assessment, who may be eligible for screening, how major lung cancer types differ, and why scan findings need clinical context.
- LupusLearn how lupus can affect different organs, how diagnosis is made, what treatment may involve, and which symptoms need urgent care.