What Is Lyme Disease?

In This Article
Table of Contents

Each year, approximately 30,000 cases of Lyme disease are reported to the Centers for Disease Control and Prevention (CDC). However, the CDC estimates that 300,000 people may get Lyme disease each year in the United States. Lyme disease is an infection caused by a bacterium called Borrelia burgdorferi that's spread to humans by infected black-legged ticks, commonly known as deer ticks. You're far more likely to contract Lyme disease in the Northeast, Mid-Atlantic, or North-Central states, as well as on the West Coast, particularly northern California. Symptoms can begin anywhere from days after you've been bitten to years afterwards.

Where Is Lyme Disease Most Common?
​Verywell / Emily Roberts

History of Lyme Disease

Lyme disease was first recognized in 1975 after researchers investigated why unusually large numbers of children were being diagnosed with juvenile rheumatoid arthritis in Lyme, Connecticut, and two neighboring towns. The researchers discovered that most of the affected children lived and played near wooded areas where ticks live. They also found that the children’s first symptoms typically started in the summer months, the height of the tick season. Several of the patients interviewed reported having a skin rash just before developing their arthritis, and many also recalled being bitten by a tick at the rash site.

Further investigations discovered that tiny deer ticks infected with the spiral-shaped bacterium or spirochete Borrelia burgdorferi were responsible for the outbreak of arthritis in Lyme. In Europe, a skin rash similar to that of Lyme disease was described in medical literature dating back to the turn of the 20th century. Lyme disease may have spread from Europe to the United States in the early 1900s, but health experts only recently recognized it as a distinct illness.

Lyme Disease Symptoms

In its early stages, Lyme disease typically causes a rash called erythema migrans, more commonly known as a "bulls-eye rash," around the bite area.

Sometimes flu-like symptoms, nerve problems, and heart problems. You should seek treatment as soon as possible if you notice any of these symptoms and you know or suspect that you could have been bitten by a tick, especially if you live in or have traveled to an area that's known for Lyme disease.


Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted to humans by infected ticks. Lyme disease cannot be inherited, but the risk of certain complications may be influenced by inherited genetic factors.


Just because you're bitten by an infected tick doesn't necessarily mean you'll contract Lyme disease. A tick bite doesn't happen in just seconds like a mosquito bite or a bee sting. A tick latches onto a person or an animal for a period of time as it sucks blood from the host. If the tick is infected, it can transmit the bacteria to the host.

The CDC says that the tick must remain attached to your body for at least 24 hours in order for you to develop Lyme disease. This is why it's recommended that you check yourself, your family members, and your pets once a day during tick season. A tick bite that lasts for less time will probably not transmit the disease.

Ticks that transmit Lyme disease in the United States (these ticks look very similar) include:

  • The black-legged or deer tick called Ixodes scapularis, which is most common in the Northeast, Mid-Atlantic, and north-central states
  • The western black-legged tick called Ixodes pacificus, which is found on the West Coast

There are many ticks located all over the world that do not carry Lyme disease, including Lone star ticks (Amblyomma americanum), the American dog tick (Dermacentor variabilis), the Rocky Mountain wood tick (Dermacentor andersoni), and the brown dog tick (Rhipicephalus sanguineus). That doesn't mean these ticks can't carry or transmit other diseases, however.

Role of Deer and Rodents

Small rodents and deer play an important role in a deer tick’s life cycle. Deer ticks lay eggs that turn into larvae that feed on mice and other small mammals. The larvae then develop into immature ticks called nymphs, which feed on small mammals and humans. Adult deer ticks usually feed on deer during the adult part of their life cycles. Both nymphs and adult ticks can transmit Lyme disease-causing bacteria.

Where Lyme Disease Is Found

Lyme disease has been reported in nearly all states in the United States, though a patient could certainly have contracted the disease in a state other than the one in which his or her case was identified. More than 95 percent of all reported cases are from these states:

  • Connecticut
  • Delaware
  • Maine
  • Maryland
  • Massachusetts
  • Minnesota
  • New Hampshire
  • New Jersey
  • New York
  • Pennsylvania
  • Rhode Island
  • Vermont
  • Virginia
  • Wisconsin

Lyme disease is also found in large areas of Asia and Europe.


Lyme disease can sometimes be diagnosed with antibody tests but is often diagnosed by your symptoms and whether you have been exposed to black-legged ticks. New tests are being developed to help give a more accurate diagnosis.


The main treatment for Lyme disease is a course of antibiotics. However, other measures may need to be taken depending on your symptoms and how long you've had the infection.


There are many ways you can prevent the tick bites that can lead to Lyme disease, ranging from how you dress to how you landscape to being vigilant about checking for ticks on a daily basis during prime tick season. A new vaccine for Lyme disease is also being worked on.

A Word From Verywell

If you've been diagnosed with Lyme disease, the good news is that appropriate treatments with antibiotics usually leads to complete recovery, even in late disease. Although Lyme disease poses many public health challenges, they are challenges the medical research community is well equipped to meet. New information on Lyme disease is accumulating at a rapid pace, thanks to the scientific research being conducted worldwide.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Lyme Disease. How many people get Lyme disease?

  2. Centers for Disease Control and Prevention. Lyme Disease. Signs and Symptoms of Untreated Lyme Disease

  3. U.S. National Library of Medicine. Genetics Home Reference. Lyme Disease

  4. Centers for Disease Control and Prevention. Lyme Disease. Lyme Disease Frequently Asked Questions (FAQ)

  5. Centers for Disease Control and Prevention. Lyme Disease. Diagnosis and Testing

  6. Centers for Disease Control and Prevention. Lyme Disease. Treatment

Additional Reading