Understanding Lyme Disease

Overview

Lyme disease is an infection caused by bacteria transmitted to humans through tick bites.
This complex illness can affect multiple systems in the body and may last from a few weeks to several years if untreated.
Fortunately, Lyme disease is treatable with effective medications, and many preventive steps can help reduce the risk of infection.

If you live in an area with a high incidence of Lyme disease and develop signs of infection, it’s important to contact your healthcare provider. Many people don't realize they’ve been bitten until symptoms appear. Early diagnosis and treatment can help prevent complications.

Symptoms of Lyme Disease

Untreated Lyme disease usually progresses through three stages: early localized, early disseminated, and late-stage Lyme disease.

Early Localized Stage

Occurs 3–30 days after a tick bite and may include:

Low-grade fever
Body aches
Swollen lymph nodes
Erythema migrans (EM) rash — appears at the bite site and expands outward, often resembling a "bull’s-eye."
About 70–80% of people with Lyme disease develop this rash, typically around 7 days after being bitten.

Note: A small rash immediately after removing a tick (the size of a dime) that doesn't expand is likely a reaction to tick saliva, not EM.

Early Disseminated Stage

Occurs days to months after the initial infection. Symptoms may include:

Fever
Fatigue
Dizziness
Headache
Muscle and joint pain
Chest pain and heart palpitations
Shortness of breath
Double vision
Encephalopathy (brain function issues)
Meningitis
Facial palsy (drooping on one or both sides of the face)

In some cases, the bacteria infect the heart, causing Lyme carditis, a serious heart rhythm disturbance. With treatment, recovery typically occurs within 1–6 weeks.

Late Lyme Disease Stage

Usually develops within a year of infection but may appear years later.
Symptoms include:

Arthritis, especially in the knees
Persistent joint pain
Neurological issues like meningitis, cognitive impairment, and facial palsy

Causes of Lyme Disease

Lyme disease is caused by the bacteria Borrelia burgdorferi and occasionally Borrelia mayonii.
These bacteria are transmitted to humans through the bite of infected black-legged ticks (deer ticks).

Key facts:

Lyme disease cases are highest in Minnesota, Wisconsin, and the Northeastern U.S.
The majority of infections occur from late spring to early fall.

After a tick bite, the bacteria spread from the bite area to other parts of the body, causing symptoms.
The bacteria especially tend to affect joints, although the exact reason is not fully understood.