Annual Probability of Lyme Disease

The CDC estimates approximately 476,000 Americans are diagnosed and treated for Lyme disease each year, making it the most common vector-borne disease in the United States. The annual incidence is about 0.1% nationally, but rates are much higher in endemic areas: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, and Wisconsin account for about 95% of cases.

Lyme disease is caused by the bacterium Borrelia burgdorferi, transmitted through bites of infected blacklegged (deer) ticks. The tick must be attached for 36-48 hours to transmit the bacterium. Early symptoms include the characteristic "bull's-eye" rash (erythema migrans, present in about 70-80% of cases), fever, fatigue, headache, and joint pain. If untreated, infection can spread to joints, heart, and nervous system.

Early treatment with antibiotics (doxycycline is first-line) is highly effective, with about 95% of patients recovering fully. However, about 10-20% of treated patients develop "Post-Treatment Lyme Disease Syndrome" with persistent symptoms lasting months to years. Prevention includes using DEET-based repellents, wearing long clothing in wooded areas, performing thorough tick checks after outdoor activities, and prompt tick removal. A Lyme disease vaccine is in Phase 3 clinical trials and may be available by 2026.