Lyme disease is a bacterial infection that spreads to humans through tick bites. There is currently no evidence to suggest that Lyme disease is contagious among humans.

In rare cases, however, pregnant women with Lyme disease can pass the infection on to the fetus.

This information comes from the Centers for Disease Control and Prevention (CDC).

This article will explain what Lyme disease is, how it spreads, some common symptoms, and how to prevent it.

An illustration of a deer tick, which can spread lyme disease, which is not contagious through human-to-human contact.Share on Pinterest
Lyme disease spreads through tick bites.

According to the CDC, there is no credible evidence to suggest that Lyme disease can pass from one human to another through physical contact. There is also no evidence that it can spread through air, food, water, or the bite of other insects.

Lyme bacteria are detectable in human bodily fluids, such as blood, joint fluid, semen, and vaginal secretions. However, scientists have not connected any case of Lyme disease to blood transfusions.

A few small studies have found weak evidence to suggest that Lyme disease may spread through sexual contact. However, the American Lyme Disease Foundation say that these studies do not prove a link between sexual contact and Lyme disease transmission.

It is possible for a person to sustain a tick bite by sleeping in the same bed as someone with a tick attached to them. Similarly, pets can carry ticks indoors, where they might bite a human, but pets cannot transmit Lyme disease to humans directly.

In rare cases, untreated Lyme disease can spread from a pregnant woman to the fetus through the placenta. There are no known adverse effects associated with taking antibiotics for Lyme disease during pregnancy.

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, a spiral-shaped species of bacteria that wild animals, such as deer, can carry. According to the CDC, Lyme disease is “the most common vector-borne disease in the United States.”

There are several subspecies of Borrelia bacteria worldwide. Another species of bacteria, called Borrelia mayonii, can also cause Lyme disease, but this is rare.

Lyme disease spreads through the bite of certain types of tick. Ticks are very small insects that feed on the blood of animals.

When a tick feeds on blood that contains B. burgdorferi bacteria, the bacteria enter the tick’s gut. The tick then acts as a carrier for the bacteria. If the tick bites a human and remains attached for 36–48 hours, the bacteria can enter the human’s bloodstream.

In most parts of the U.S., Lyme disease spreads via the blacklegged tick (Ixodes scapularis). Along the Pacific coast, however, the disease tends to spread via the western blacklegged tick (Ixodes pacificus).

Most humans with Lyme disease get it from immature ticks, or nymphs, which are less than 1 inch (2 millimeters) in diameter and most active during late spring and summer. These ticks can be difficult to see, and they often favor warm, moist areas of the body, including the armpits, groin, and scalp.

Lyme disease can be difficult to diagnose because it causes symptoms that are similar to those of many other illnesses.

Symptoms tend to appear around 3–30 days after the tick bite. The most recognizable symptom of Lyme disease is a skin rash that develops around the tick bite and resembles a target. Doctors call this rash erythema migrans (EM).

EM begins as a small rash that may be warm to the touch, gradually expanding in size by up to 12 inches (30 centimeters). It usually appears within 7 days of a tick bite. Around 70–80% of people with Lyme disease will develop EM.

Some other common signs and symptoms of Lyme disease that can occur with or without a rash include:

  • fever and chills
  • headaches
  • unexplained fatigue
  • muscle and joint pain
  • swollen lymph nodes

Later stage signs and symptoms of Lyme disease include:

  • severe headaches
  • neck stiffness
  • loss of facial muscle tone
  • additional EM rashes
  • pain and swelling in the tendons, muscles, joints, nerves, and bones
  • dizziness
  • shortness of breath
  • pain, numbness, or tingling in the hands and feet
  • swelling of the brain and spinal cord
  • an irregular heartbeat or heart palpitations

A doctor may suspect Lyme disease based on a person’s symptoms and the likelihood that they have encountered a blacklegged tick. If they do suspect Lyme disease, they may order a Lyme disease blood test to confirm it.

Lyme disease blood tests work by detecting Lyme antibodies, which can take several weeks to develop after a tick bite. A single test does not always provide a clear diagnosis, so the CDC recommend that doctors perform two.

If the first test is negative, a person does not have detectable Lyme antibodies in their blood. If the result is “indeterminate,” the doctor will perform a second test. A person has a firm diagnosis when both tests give either positive or indeterminate results.

It is worth noting that other viral, bacterial, and autoimmune conditions can sometimes cause false-positive results in Lyme disease blood tests.

Doctors treat early stage Lyme disease with antibiotics, such as doxycycline, amoxicillin, or cefuroxime. Courses often last 2–4 weeks. Most people will feel better within a few weeks of Lyme disease treatment.

Later stage Lyme disease can be more difficult to treat. In these cases, doctors may use intravenous antibiotics or prescribe antibiotics for longer periods of time.

Some people develop chronic symptoms that last for longer than 6 months after Lyme disease treatment. People call this chronic Lyme disease, or post-treatment Lyme disease syndrome (PTLDS).

Scientists do not yet know why some people develop PTLDS. Some experts believe that it is due to an autoimmune response. Others believe that it is the result of a persistent but difficult-to-detect infection.

Currently, there are no effective treatments for PTLDS. However, people often recover from PTLDS over time.

The most effective way to prevent Lyme disease is to prevent exposure to blacklegged ticks. People can do this by:

  • familiarizing themselves with where ticks may live
  • limiting the time they spend in tick-prone areas
  • walking in the center of paths and trails
  • avoiding wooded, bushy areas with tall grass or leaf litter
  • treating all clothing, footwear, and camping equipment with 0.5% permethrin
  • wearing long pants and long-sleeved tops when outdoors
  • using insect repellents, such as oil of lemon eucalyptus (OLE), diethyltoluamide, or para-menthane-3,8-diol (PMD).

Products containing OLE or PMD are not safe for use in children under 3 years of age.

After spending time outdoors, people can reduce the risk of Lyme disease by:

  • thoroughly checking all clothing, gear, and pets for ticks before going indoors
  • checking the body for ticks, particularly hard-to-see areas, such as the hair, ears, armpits, backs of the knees, and between the legs
  • removing any ticks safely using tweezers, then cleaning the area and the hands with soap and water
  • washing all exposed clothes with hot water or tumble-drying them on a high heat for at least 10 minutes
  • taking a shower within 2 hours of going indoors
  • treating pets or other animals that may have exposure to ticks with veterinarian-approved anti-tick medications

A person can store any ticks they find on their skin or clothes in alcohol, a sealed bag, or wrapped tightly in tape. This can help later if a doctor needs to identify the species.

People can discourage ticks from living in their yard by:

  • clearing tall grasses and bushes
  • mowing any lawns frequently
  • raking leaves often
  • removing old furniture or trash from yards
  • creating a wood chip or gravel barrier that is around 3 feet (0.9 meters) wide around used spaces
  • keeping used spaces as sunny as possible
  • stacking wood in a dry area

Anyone who has unexplained symptoms or thinks that they have had exposure to Lyme disease should talk with a doctor as soon as possible. Later stage Lyme disease can affect the joints, heart, and nervous system, so it is important to treat it early with antibiotics.

Lyme disease spreads through the bite of the blacklegged tick. Currently, there is no reliable evidence to suggest that Lyme disease is contagious among humans. It also does not spread through air, water, or food.

Anyone who has unexplained symptoms after sustaining a tick bite should talk with a doctor as soon as possible to prevent serious complications.