Lyme disease, also known as borreliosis, is an infection by the bacterium Borrelia burgdorferi. The bacterium is transmitted to humans when they are bitten by an infected tick.
Lyme disease is the most common tick-borne infectious disease in the United States.
The CDC registered 25,359 confirmed cases of Lyme disease and 8,102 probable cases in 2014.
The CDC estimate that approximately 300,000 cases of Lyme disease are reported by state health departments each year.
Contents of this article:
Fast facts on Lyme disease
Here are some key points about Lyme disease. More detail and supporting information is in the main article.
- Lyme disease is the most common tick-borne disease in the U.S.
- The disease cannot be passed through breast milk
- A common symptom of Lyme disease is an erythema migrans rash
How is Lyme disease transmitted?
A blacklegged tick, formerly known as the deer tick.
In the United States, Borrelia burgdorferi, the Lyme disease-causing bacterium, enters humans through the bite of:
- An infected blacklegged tick (Ixodes scapularis)
- An infected western blacklegged tick (Ixodes pacificus)
The adult tick or the young nymph bores a tiny hole in the skin and inserts its mouthparts into the opening, attaching itself to the host. Ticks tend to attach to hard-to-see areas of the human body, such as the scalp, armpits, and groin.
Generally, the tick must remain attached for at least 36-48 hours before transmitting the Borrelia burgdorferi bacterium into a human.
People tend to get rid of the larger adults before they have time to transmit the bacterium, so most human infections occur as a result of bites from barely visible nymphs.
If you find a tick attached to yourself, use our guide to removing them safely.
Lyme disease transmission FAQ
Here we answer some of the most frequently asked questions about Lyme disease:
1) Can Lyme disease spread from human-to-human?
No. You cannot become infected by touching, kissing, or having sex with an infected person.
2) What happens if I am pregnant and have Lyme disease?
There are a number of small studies and case reports linking Lyme disease in pregnancy to birth defects or fetal demise (death of the fetus before it is born). However, there has not been enough research to definitively conclude that Lyme disease negatively affects pregnancy.
Antibiotic treatment given to a pregnant mother for Lyme disease does not affect the fetus; the treatment will be different than the standard antibiotics used in non-pregnant adults.
3) Can I breast-feed if I have Lyme disease?
The CDC say that there are no reports of Lyme disease transmission from breast milk.
The National Health Service (NHS), United Kingdom, say that the Lyme disease-causing bacterium cannot be passed on through breast milk.
4) Can Lyme disease be transmitted through blood transfusion?
There is a theoretical risk, but experts say this is highly unlikely.
5) Can my dog or cat transmit Lyme disease?
Dogs and cats can get Lyme disease. However, they cannot infect humans. It is important to check your pets for ticks because they can bring them into the house.
6) Can I get Lyme disease from eating venison?
According to the Missouri Department of Conservation, "there has never been a documented case of a human contracting Lyme disease through the handling or consumption of venison."
7) Can I get Lyme disease from the environment?
You cannot get Lyme disease from the air, food, or water. Also, it is not possible to become infected from the bites of lice, mosquitoes, fleas, or flies. Lyme disease is transmitted primarily through the Ixodes tick.
Symptoms of Lyme disease
Initial signs and symptoms of Lyme disease are usually very mild. In fact, many people may notice nothing at all, unless they are aware of the telltale signs. If someone suspects Lyme disease, they should get medical help immediately. Early treatment is much more effective.
There are three recognized phases of Lyme disease:
Early Lyme disease (stage 1)
Erythema migrans rash in the pattern of a "bull's-eye."
Erythema migrans (EM) refers to a rash that often appears in the early stage of Lyme disease.
- The EM rash typically begins as a small red area which expands over a period of several days. It may eventually reach a diameter of 12 inches (30 centimeters). The rash is less evident in people with dark skin.
- The center of the rash will likely lose its color, giving the whole area a bull's-eye appearance.
- The most common areas for the rash are the armpits, trunk, groin, buttocks, scalp, the nape of the neck, and thighs. It usually starts off at the site of the tick bite, but not always.
- The rash usually feels warm when touched (not always).
- There is no pain or itchiness.
- As Borrelia burgdorferi bacteria circulate through the blood, patches of rash may appear in other parts of the body.
- The rash gradually clears up after about 4 weeks, even if the Lyme disease is left untreated.
Other symptoms may occur at the same time as the rash, including fever, swollen lymph nodes, fatigue, chills, and joint pains. However, in most cases, the affected person may not perceive them as serious enough to see a doctor.
Early disseminated Lyme disease (stage 2)
If left untreated, the bacteria may spread elsewhere in the body and cause a range of symptoms. This stage appears weeks to months after initial infection.
Signs and symptoms may include:
- Other Erythema migrans rashes. These can appear anywhere and may show up on multiple parts of the body.
- Bell's palsy - the muscles on one side of the face lose their tone.
- Meningitis - spinal cord inflammation. The patient experiences painful headaches and a stiff neck.
- The large joints, such as the knees, become painful and swollen.
- Numbness and/or shooting pains in the arms and legs - in some cases the patient may find it hard to sleep.
- In rare cases, abnormal heartbeat.
In most cases, within a few weeks or months, these symptoms will gradually go away, even if the patient remains untreated.
However, if no proper treatment is administered, complications may develop.
Late disseminated Lyme disease (stage 3)
This stage is also known as late Lyme disease. In untreated patients, it can occur weeks, months, and even years after initial infection. In some patients, this may even be the initial presentation.
Even treated patients whose antibiotics did not kill off all the bacteria can reach this stage. Symptoms include:
- Arthritis - around 25 percent of untreated patients will have recurrent bouts of arthritis with severe joint swelling, especially of the large joints.
- Difficulty concentrating.
- Unrestful sleep.
- Memory loss or cognitive impairment.
- Tingling and/or numbness in the hands or feet.
Diagnosing Lyme disease
Ideally, treatment should occur as soon as the EM rash appears. Even if there is no rash, the post-Lyme disease syndrome (resource no longer available at www.aldf.com) (sometimes referred to as chronic Lyme disease). This syndrome is a descriptive term for nonspecific symptoms, like arthralgias (joint pain), that can persist for months after treatment.
It is important to note that the symptoms are not due to an active infection itself. The primary treatment is supportive care (like rest and anti-inflammatory medications), the symptoms should resolve on their own over time.