Lyme disease is an infection caused by bacteria that tick bites transmit to humans

Lyme disease begins when an infected tick bites you and passes Borrelia burgdorferi bacteria into your bloodstream. Not all ticks carry the bacteria—only certain species do, primarily the deer tick (also called the black-legged tick). The tick has to stay attached to your skin for a period of time to transmit the infection; a tick that falls off within the first 24 hours is unlikely to pass the bacteria. Once infected, the bacteria spread through your body and can affect your joints, heart, nervous system, and skin.

The infection is not contagious from person to person. You cannot catch Lyme disease from someone who has it, and a person with Lyme disease cannot spread it to others through contact, saliva, or blood. The only way to get Lyme disease is through a tick bite from an infected tick.

Key Takeaways

  • Lyme disease comes from bacteria in tick saliva that enters your body during a bite, not from the tick itself.
  • The tick must be attached for several hours to transmit the infection, so removing a tick within 24 hours greatly reduces your risk.
  • Early signs include a rash that often looks like a bullseye, fever, chills, and body aches that appear days to weeks after the bite.
  • Without treatment, Lyme disease can progress to affect your joints, heart, and nervous system, causing long-term problems.
  • Lyme disease is diagnosed through blood tests and treated with antibiotics, which work best when started early.

Early symptoms: the rash and flu-like signs

The first sign of Lyme disease is often a rash called erythema migrans, which appears at the site of the tick bite. This rash typically shows up 3 to 30 days after infection and grows outward in a circular pattern. Many people describe it as looking like a bullseye—a red center surrounded by a clear ring and then another red ring—though not all rashes look this way. Some are solid red, and some never appear at all.

Along with the rash, you may develop flu-like symptoms: fever, chills, fatigue, headache, muscle aches, and joint pain. These symptoms can start at the same time as the rash or appear separately. Some people have only the rash and no other symptoms in the early stage. Others feel sick but never develop a rash, which is why Lyme disease is sometimes missed at first.

What happens if Lyme disease goes untreated

If the infection is not treated with antibiotics, the bacteria continue to spread and can cause problems weeks or months later. Late-stage Lyme disease can affect multiple parts of your body. Arthritis is common, especially in the knees, causing swelling and pain that may come and go. Some people develop neurological problems—nerve pain, numbness, weakness, or facial paralysis on one side of the face (called Bell's palsy). Heart problems can occur but are less common and usually mild.

The longer the infection goes untreated, the more damage the bacteria can do. This is why early detection and treatment matter. Starting antibiotics in the first few weeks of infection stops the bacteria from spreading and prevents these later complications.

How Lyme disease is diagnosed

Diagnosis starts with your medical history and a physical exam. Your doctor will ask whether you remember a tick bite, when the bite occurred, and what symptoms you have. If you have the characteristic bullseye rash, diagnosis can be made on appearance alone without testing.

When the rash is unclear or absent, blood tests are used to look for antibodies your immune system makes in response to the bacteria. Two types of blood tests are standard: an ELISA test (enzyme-linked immunosorbent assay) screens for Lyme disease, and a Western blot test confirms a positive result. These tests work best if done at least a week or two after infection, because your body needs time to produce detectable antibodies. Testing too early may give a false negative result.

Treatment with antibiotics

Lyme disease is treated with antibiotics that kill the bacteria. The type of antibiotic and length of treatment depend on how far the infection has progressed and which parts of your body are affected. Early-stage Lyme disease is usually treated with oral antibiotics (taken by mouth) for 14 to 21 days. Doxycycline is the most common choice for adults and older children; amoxicillin or cefuroxime are used for pregnant people and young children.

If Lyme disease has progressed to affect the nervous system or heart, intravenous antibiotics (given through a vein) may be needed. Treatment started early is highly effective at stopping the infection and preventing complications. Even if you have had Lyme disease for months, antibiotics can still help, though recovery may take longer.

Where Lyme disease is most common

Lyme disease is found across the United States, but the risk is highest in the Northeast, Mid-Atlantic, and upper Midwest. States like New York, Pennsylvania, New Jersey, Connecticut, Massachusetts, and Minnesota report the most cases. The disease is also common in parts of Europe and Asia. In areas where infected ticks are present, the risk is highest during spring and summer months when ticks are most active, though tick bites can happen year-round.

Your personal risk depends on where you live and how much time you spend outdoors in wooded or grassy areas where ticks live. Even in high-risk areas, most tick bites do not result in Lyme disease, because not all ticks are infected.

Prevention: removing ticks and reducing exposure

The most effective way to prevent Lyme disease is to remove ticks promptly. If you find a tick on your skin, use fine-tipped tweezers to grasp it as close to the skin as possible and pull straight out with steady pressure. Do not twist, squeeze, or jerk the tick, as this can leave the mouthparts in your skin or cause the tick to release bacteria. After removal, wash the area with soap and water. Removing a tick within 24 hours greatly reduces the chance of infection.

To reduce your exposure to ticks, wear long sleeves and long pants when in wooded or grassy areas, tuck your pants into your socks, and use insect repellent containing DEET on exposed skin. Check your entire body for ticks after being outdoors, paying special attention to warm, moist areas like the groin, armpits, and behind the knees. Ticks are small and can be easy to miss, so a thorough check matters.

Frequently Asked Questions

Can you get Lyme disease from a tick that is not attached to your skin?

No. A tick must bite and attach to your skin to transmit the bacteria. A tick crawling on your clothing or skin without biting cannot give you Lyme disease. This is why removing a tick quickly—even within a few hours—is effective prevention.

What should I do if I think I have Lyme disease?

Contact your primary care doctor or visit an urgent care clinic. Bring information about when and where you were bitten if you know it, and describe your symptoms. If you have the bullseye rash, take a photo to show your doctor. Early treatment with antibiotics is most effective, so do not wait.

If I had Lyme disease once, can I get it again?

Yes. Having Lyme disease once does not make you immune. You can be infected again if bitten by another infected tick. Prevention measures—prompt tick removal and protective clothing—matter every time you are outdoors in tick-prone areas.

Is there a vaccine for Lyme disease?

A vaccine called LYMErix was available in the United States but was withdrawn from the market in 2002 due to low demand. No Lyme disease vaccine is currently available in the United States, though research into new vaccines is ongoing. Prevention through tick avoidance and removal remains the main strategy.