Lyme Disease

Lyme Disease Bacteria, Borrelia burgdorferi

The Lyme disease spirochete, Borrelia burgdorferi, is an obligate parasite that cycles between ticks and vertebrate hosts. B. burgdorferi alters the proteins expressed on its outer surface, depending on the state.

Credit: NIAID

Lyme disease, or borreliosis, is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of an infected blacklegged deer tick. It is the most common tickborne infectious disease in the United States.  

Why Is the Study of Lyme Disease a Priority for NIAID?

State health departments reported 42,743 confirmed or probable cases to the Centers for Disease Control and Prevention (CDC) in 2017.  Reported cases are not believed to reflect the actual incidence of Lyme disease, and CDC estimates that 300,000 cases likely occur annually. The incidence of Lyme disease, as with many other tick-borne diseases, has increased dramatically over the past 10 years.

How Is NIAID Addressing This Critical Topic?

NIAID has a long-standing commitment to conduct research on Lyme borreliosis, or Lyme disease, beginning more than 35 years ago when the cause of the disease was not yet known. In 1981, NIAID-funded research efforts resulted in identifying Borrelia burgdorferi, a spiral-shaped bacterium, or spirochete, as the causative agent of Lyme disease. Since then, basic and clinical research efforts have been expanded in scope to address many different aspects of this infectious disease. Read more about how NIAID is addressing Lyme disease.

To learn about risk factors for Lyme Disease and current prevention and treatment strategies visit the MedlinePlus Lyme Disease site.


NIAID is committed to improving Lyme disease diagnostics by supporting innovative research projects. Priorities include finding potential targets—substances that new diagnostic tools might measure in patient samples—and improving the sensitivity and specificity of currently available diagnostic tests, thereby leading to more accurate results.

Antibiotic Treatment for Early Lyme Disease

For early Lyme disease, a short course of oral antibiotics, such as doxycycline or amoxicillin, cures the majority of cases. In more complicated cases, Lyme disease can usually be successfully treated with three to four weeks of antibiotic therapy.

Chronic Lyme Disease

In patients who have non-specific symptoms after being treated for Lyme disease and who have no evidence of active infection (patients with PTLDS, post-treatment Lyme disease syndrome), studies have shown that more antibiotic therapy is not helpful and can be dangerous.


Ticks can become infected with more than one disease-causing microbe (called co-infection). Co-infection may be a potential problem for humans, because the Ixodes ticks that transmit Borrelia burgdorferi, the bacterium which causes Lyme disease, often carry and transmit other pathogens, as well. A single tick could make a person sick with any one—or several—diseases at the same time.


NIAID supports significant research efforts focused on human vaccination against Lyme disease. Ongoing research activities include multiple research projects in early-stage discovery and characterization of novel vaccine formulations and targets, including tick saliva-based approaches.

Clinical Trials

NIAID supports clinical research trials to develop better ways of diagnosing, treating, and preventing Lyme disease. People who have been diagnosed with Lyme disease or who suspect that they have Lyme disease may be eligible to participate.


Content last reviewed on November 16, 2018