Lyme disease is an infection caused by the bacterium Borrelia burgdorferi transmitted primarily by blacklegged ticks. Recognition of common symptoms is important for timely diagnosis and treatment because early therapy usually prevents the more serious complications associated with untreated infection. The Centers for Disease Control and Prevention emphasizes that clinical signs and laboratory testing together guide diagnosis, while Allen C. Steere Massachusetts General Hospital historically characterized the expanding skin lesion that often signals early infection.
Early symptoms
The most recognizable early sign is erythema migrans, an expanding skin redness that may form a central clearing and classic “bull’s-eye” appearance, although not every patient develops the textbook pattern. The Centers for Disease Control and Prevention notes that many people also experience systemic, flu-like symptoms in early localized infection, including fever, chills, headache, fatigue, muscle aches, and swollen lymph nodes. These symptoms can appear within days to weeks after a tick bite and may be mild or mistaken for a viral illness. Mayo Clinic Staff Mayo Clinic explains that early recognition of the rash and accompanying symptoms increases the likelihood of effective antibiotic treatment.
Later symptoms and complications
If infection is untreated, Borrelia burgdorferi can spread and cause neurologic, cardiac, and arthritic manifestations. Neurologic involvement may include facial nerve palsy (Bell’s palsy), meningitis, or radicular pain, and Lyme arthritis commonly produces intermittent or persistent swelling and pain in large joints such as the knee. Cardiac manifestations are less common but can include atrioventricular conduction block. The Centers for Disease Control and Prevention describes this progression and highlights the variable timing and severity of later-stage symptoms. Research by John Aucott Johns Hopkins University has examined persistent symptoms reported by some patients after standard antibiotic treatment, a phenomenon referred to as post-treatment Lyme disease symptoms, and underscores ongoing debates about mechanisms and management.
Geography and environment shape risk: the infection is most commonly reported in the northeastern, mid-Atlantic, and upper Midwestern United States because of blacklegged tick habitat and human exposure patterns. Cultural and occupational factors such as outdoor work, recreational activities, and local awareness influence both exposure and how quickly people seek care. Access to prompt medical evaluation varies by region and community, which affects outcomes.
Diagnosis can be complicated early because antibody tests may be negative in the first weeks; clinicians rely on clinical presentation and exposure history together with testing. Untreated Lyme disease can cause prolonged disability in some cases, so timely assessment and appropriate antibiotic treatment remain central to preventing complications.