Lyme Disease: Symptoms, Causes & Treatment Guide

What Is Lyme Disease?

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, transmitted to humans through the bite of infected blacklegged ticks (also called deer ticks). It is the most common vector-borne disease in the Northern Hemisphere, with approximately 476,000 cases diagnosed annually in the United States alone.

Lyme disease, also known as Lyme borreliosis, was first recognized in 1975 after a cluster of arthritis cases in children in Lyme, Connecticut led researchers to identify the bacterial cause and its tick vector. The disease has since been found throughout temperate regions of North America, Europe, and Asia, with the highest incidence in the northeastern and upper midwestern United States, and in central and northern Europe.

The bacteria responsible for Lyme disease belong to the Borrelia genus, a group of spiral-shaped bacteria called spirochetes. In North America, Borrelia burgdorferi is the primary cause, while in Europe, Borrelia afzelii and Borrelia garinii also cause the disease, which can lead to slightly different symptom patterns. These bacteria are transmitted to humans through the bite of infected Ixodes ticks – primarily the blacklegged tick (Ixodes scapularis) in the eastern United States, the western blacklegged tick (Ixodes pacificus) on the Pacific Coast, and Ixodes ricinus (the castor bean tick or sheep tick) in Europe.

Understanding the tick's life cycle is important for prevention. Ticks have four life stages: egg, larva, nymph, and adult. Most human infections occur from nymphal ticks, which are most active during late spring and summer and are very small (about the size of a poppy seed), making them difficult to detect. The tick must typically be attached for 36 to 48 hours before the bacteria can be transmitted, which is why prompt tick removal is so effective at preventing infection.

Geographic Distribution

Lyme disease occurs primarily in temperate climates where the tick vectors thrive. In North America, the disease is concentrated in the Northeast (from Virginia to Maine), the upper Midwest (Wisconsin and Minnesota), and the Pacific Coast. In Europe, the highest incidence is in central European countries including Germany, Austria, and Slovenia, as well as in Scandinavia. The disease is also found in parts of Asia, including China, Japan, and South Korea.

Climate change is expanding the geographic range of ticks, and Lyme disease cases have been reported in areas previously considered low-risk. This makes awareness and prevention important even in regions where Lyme disease was historically rare.

What Are the Symptoms of Lyme Disease?

Lyme disease symptoms typically progress in stages. The earliest and most recognizable sign is a red, expanding rash called erythema migrans that appears at the bite site within 3-30 days. Early symptoms also include fever, fatigue, headache, and muscle aches. If untreated, the infection can spread to joints, the heart, and the nervous system.

Lyme disease manifests in distinct stages, though not everyone experiences all stages, and the progression can vary significantly between individuals. Understanding these stages helps with early recognition and timely treatment, which dramatically improves outcomes.

Early Localized Stage (Days to Weeks After Bite)

The hallmark of early Lyme disease is erythema migrans, a characteristic skin rash that develops at the site of the tick bite. This rash appears in approximately 70-80% of infected individuals and is considered diagnostic of Lyme disease – meaning if a doctor sees this rash, they can diagnose Lyme disease without waiting for blood test results.

The erythema migrans rash has several distinctive characteristics. It typically begins as a small red spot that gradually expands over days to weeks, often reaching 12 inches (30 cm) or more in diameter. As it expands, the center may clear, creating the characteristic "bull's-eye" or target-like appearance, though this classic pattern is not always present. The rash is usually not painful or itchy, though it may feel warm to the touch. On darker skin tones, the rash may be harder to see and can appear more like a bruise.

Along with the rash, many people experience flu-like symptoms during this early stage, including fever, chills, fatigue, headache, muscle and joint aches, and swollen lymph nodes near the tick bite. These symptoms can come and go and may be mistaken for a viral illness.

Early Disseminated Stage (Weeks to Months After Bite)

If untreated, the bacteria can spread through the bloodstream to other parts of the body. This stage may occur days to weeks after the initial infection. Signs of disseminated Lyme disease include:

• Multiple erythema migrans lesions: Smaller rashes appearing on other parts of the body, indicating blood-borne spread
• Neurological symptoms: Facial paralysis (Bell's palsy), meningitis with severe headache and neck stiffness, numbness or tingling in the limbs
• Cardiac involvement (Lyme carditis): Inflammation of the heart causing irregular heartbeat, palpitations, dizziness, or fainting
• Joint pain: Brief episodes of pain and swelling, particularly in large joints like the knee
• Eye inflammation: Conjunctivitis or other forms of eye involvement

Neurological involvement, called neuroborreliosis, is more common in children than adults. It can cause facial paralysis that may affect one or both sides of the face, meningitis (inflammation of the membranes surrounding the brain), and radiculopathy (nerve root inflammation causing radiating pain). These symptoms can be alarming but typically respond well to antibiotic treatment.

Late Disseminated Stage (Months to Years After Bite)

Without treatment, Lyme disease can progress to late-stage manifestations months to years after the initial infection. The most common late manifestation is Lyme arthritis, which typically affects large joints, especially the knee. The arthritis causes episodes of swelling and pain that can last for weeks to months and may recur. In some cases, the arthritis can become chronic even after antibiotic treatment.

Late neurological Lyme disease can cause encephalopathy (affecting memory, concentration, and mood), peripheral neuropathy (numbness and tingling in the hands and feet), and chronic fatigue. A rare but distinctive late skin manifestation called acrodermatitis chronica atrophicans can occur, primarily in European patients, causing bluish-red discoloration and swelling of the skin, usually on the extremities, which eventually leads to thin, atrophic skin.

When Should You See a Doctor for Lyme Disease?

See a doctor if you develop a red, expanding rash (especially with a bull's-eye pattern) after spending time in tick-prone areas, or if you experience flu-like symptoms weeks after a known or possible tick bite. Seek immediate care for facial paralysis, severe headache with neck stiffness, or heart palpitations.

Early diagnosis and treatment of Lyme disease leads to the best outcomes. While not every tick bite requires medical attention, certain situations warrant prompt evaluation by a healthcare provider. Understanding when to seek care can help prevent the progression to more serious stages of the disease.

You should schedule an appointment with a doctor if you notice a red rash expanding outward from a tick bite site or appearing anywhere on your body after spending time outdoors in areas where ticks are common. The erythema migrans rash is diagnostic of Lyme disease, and treatment can begin immediately without waiting for blood test results. Even if you don't remember being bitten by a tick (many people don't notice the bite), an expanding rash warrants evaluation.

Flu-like symptoms that develop within several weeks of possible tick exposure should also prompt a medical visit. This includes fever, fatigue, headache, muscle aches, and joint pain, especially if they persist or occur during tick season after outdoor activities in endemic areas.

Emergency Symptoms

Certain symptoms of Lyme disease require urgent or emergency medical care. If you experience severe headache combined with neck stiffness and light sensitivity, this could indicate meningitis and requires immediate evaluation. Facial paralysis or drooping, where one side of your face becomes weak or paralyzed, can be a sign of Lyme neuroborreliosis and needs prompt treatment to prevent lasting damage.

Heart symptoms including chest pain, shortness of breath, irregular heartbeat, or fainting spells could indicate Lyme carditis, a potentially serious complication that can cause heart block. While Lyme carditis is rare (occurring in about 1% of untreated cases), it can be life-threatening and requires immediate medical attention.

After a Tick Bite

Finding an attached tick can be concerning, but not every tick bite requires antibiotic prophylaxis. The decision to treat preventively depends on several factors: the type of tick (only blacklegged ticks transmit Lyme disease), how long the tick was attached (transmission typically requires 36+ hours of attachment), and whether you're in an area where Lyme disease is common.

In high-risk situations – when an identified blacklegged tick has been attached for more than 36 hours in an endemic area – a single dose of doxycycline may be given within 72 hours of tick removal to prevent Lyme disease. However, this is not routinely recommended for all tick bites. Your healthcare provider can help determine whether preventive treatment is appropriate based on your specific circumstances.

What Causes Lyme Disease?

Lyme disease is caused by spiral-shaped bacteria called Borrelia burgdorferi (in North America) or Borrelia afzelii and Borrelia garinii (in Europe). These bacteria are transmitted to humans through the bite of infected blacklegged ticks (Ixodes species). The tick must typically be attached for 36-48 hours for transmission to occur.

Understanding how Lyme disease is transmitted is essential for prevention. The disease involves a complex ecological cycle involving ticks, their animal hosts, and the Borrelia bacteria. This cycle has adapted over millions of years and operates efficiently in certain environmental conditions.

The bacteria that cause Lyme disease are spirochetes, a type of bacteria with a distinctive spiral or corkscrew shape that allows them to move efficiently through tissues. Borrelia burgdorferi is the primary species in North America, while Borrelia afzelii and Borrelia garinii are more common in Europe and Asia. These different species can cause slightly different symptom patterns – for example, B. afzelii is more associated with skin manifestations, while B. garinii more commonly causes neurological symptoms.

The Tick Vector

Lyme disease is transmitted exclusively through the bite of infected Ixodes ticks. In the eastern and central United States, the blacklegged tick (Ixodes scapularis), often called the deer tick, is the primary vector. On the Pacific Coast, the western blacklegged tick (Ixodes pacificus) transmits the disease. In Europe, the castor bean tick or sheep tick (Ixodes ricinus) is responsible, while in Asia, Ixodes persulcatus is the main vector.

Ticks are not born infected with Borrelia bacteria. Instead, they acquire the bacteria when feeding on infected animal hosts during their larval or nymphal stages. White-footed mice are the primary reservoir hosts in North America – these mice can carry the bacteria in their blood without becoming ill. When a tick feeds on an infected mouse, it picks up the bacteria and can then transmit them to its next host, which might be another mouse, a larger animal, or a human.

The name "deer tick" is somewhat misleading. While adult ticks often feed on deer, deer are not infected with Borrelia and cannot transmit the bacteria. However, deer play an important role in the tick life cycle by serving as hosts for adult ticks to feed and mate on. Areas with large deer populations tend to have higher tick populations.

Transmission Process

When an infected tick bites a human, it doesn't immediately transmit the bacteria. The Borrelia organisms live in the tick's gut and must migrate to its salivary glands before they can be transmitted during feeding. This process takes time, which is why the tick typically needs to be attached for 36 to 48 hours before transmission occurs. Some studies suggest that the risk becomes significant after 24 hours but increases substantially with longer attachment times.

This delay in transmission is actually good news for prevention – if you find and remove a tick quickly, your risk of infection is very low. Daily tick checks after spending time outdoors in endemic areas can effectively prevent most Lyme disease cases.

How Is Lyme Disease Diagnosed?

Lyme disease is diagnosed based on symptoms, history of tick exposure, and blood tests. The characteristic erythema migrans rash is diagnostic on its own. For other presentations, a two-step blood test (ELISA followed by Western blot) detects antibodies against Borrelia. Testing may be negative in the first few weeks of infection.

Diagnosing Lyme disease can be straightforward when the characteristic rash is present, but it becomes more challenging when the rash is absent or when patients present with later-stage symptoms. A combination of clinical assessment and laboratory testing is used to make the diagnosis.

Clinical Diagnosis

The erythema migrans rash is considered pathognomonic (definitively diagnostic) for Lyme disease. When a healthcare provider sees this characteristic expanding rash in a patient with a history of possible tick exposure, they can diagnose Lyme disease and begin treatment without waiting for laboratory confirmation. Blood tests at this early stage are often negative because the body hasn't yet produced detectable antibodies.

For patients without the rash, diagnosis relies more heavily on clinical judgment. Doctors consider the patient's symptoms, history of possible tick exposure, geographic location, and time of year. They also rule out other conditions that might cause similar symptoms.

Laboratory Testing

The standard laboratory approach to Lyme disease diagnosis is two-tier serological testing recommended by the CDC. This involves first performing an enzyme-linked immunosorbent assay (ELISA) or immunofluorescence assay (IFA) to screen for antibodies against Borrelia. If this initial test is positive or equivocal, it is followed by a Western blot test to confirm the presence of specific antibodies.

It's important to understand that these tests detect the body's immune response to the bacteria, not the bacteria themselves. This means that tests may be negative during the first few weeks of infection before antibodies have developed. A person tested very early in the course of Lyme disease may have a false-negative result. If clinical suspicion is high, the test may need to be repeated after several weeks.

Antibodies to Borrelia can persist for months to years after successful treatment, so a positive antibody test doesn't necessarily indicate active infection. This is why testing is not useful for monitoring treatment response or determining if a previous infection has been cured.

Testing for Neuroborreliosis

When Lyme disease is suspected to have spread to the nervous system, additional testing may be needed. A lumbar puncture (spinal tap) can be performed to analyze cerebrospinal fluid (CSF) for signs of inflammation and for antibodies produced within the nervous system. Finding antibodies in the CSF that are higher than would be expected based on blood levels suggests active infection within the nervous system.

Testing for Lyme Arthritis

For suspected Lyme arthritis, joint fluid may be analyzed to look for signs of inflammation and to rule out other causes of joint swelling. PCR (polymerase chain reaction) testing of joint fluid can sometimes detect Borrelia DNA, though this test is not always positive even in confirmed cases.

How Is Lyme Disease Treated?

Lyme disease is treated with antibiotics. Early-stage Lyme disease responds well to 10-21 days of oral antibiotics such as doxycycline, amoxicillin, or cefuroxime. More serious cases involving the heart or nervous system may require intravenous antibiotics. The vast majority of patients recover completely with appropriate treatment.

The treatment of Lyme disease has been extensively studied, and antibiotics are highly effective, especially when started early in the course of infection. The choice of antibiotic, route of administration, and duration of treatment depend on the stage of disease and which organ systems are affected.

Treatment of Early Lyme Disease

For early localized and early disseminated Lyme disease without significant neurological or cardiac involvement, oral antibiotics are the treatment of choice. The most commonly used medications include:

• Doxycycline: 100 mg twice daily for 10-21 days. This is the preferred treatment for adults because it also treats other tick-borne infections that may be transmitted simultaneously.
• Amoxicillin: 500 mg three times daily for 14-21 days. Preferred for children under 8, pregnant women, and those who cannot take doxycycline.
• Cefuroxime axetil: 500 mg twice daily for 14-21 days. An alternative for patients allergic to penicillin but not to cephalosporins.

With early treatment, most patients see improvement within a few days to weeks. The erythema migrans rash typically resolves within 1-2 weeks of starting antibiotics, though it may initially appear to expand slightly before fading. Flu-like symptoms usually improve quickly as well.

Treatment of Neurological Lyme Disease

Patients with neurological manifestations such as meningitis, encephalitis, or significant radiculopathy may require intravenous antibiotics. Ceftriaxone (2 grams once daily) is typically given for 14-28 days. However, some studies suggest that oral doxycycline may be equally effective for certain neurological presentations, particularly in Europe where it is more commonly used.

Facial paralysis (Bell's palsy) due to Lyme disease can often be treated with oral antibiotics alone, though this should be evaluated on a case-by-case basis. Most patients with Lyme-related facial paralysis recover completely, though improvement may take weeks to months.

Treatment of Lyme Carditis

Lyme carditis requires careful monitoring because it can cause serious heart rhythm disturbances. Patients with mild carditis (first-degree heart block with minimal PR prolongation) may be treated with oral antibiotics. Those with more severe heart block require hospitalization for cardiac monitoring and are treated with intravenous antibiotics, typically ceftriaxone. In rare cases, temporary pacing may be necessary, but permanent pacemaker implantation is almost never required because the heart block resolves with treatment.

Treatment of Lyme Arthritis

Lyme arthritis is initially treated with a 28-day course of oral antibiotics (doxycycline or amoxicillin). Many patients respond to this treatment with resolution of joint swelling and pain. If symptoms persist after one course of oral antibiotics, a second course or a course of intravenous antibiotics may be tried.

Some patients develop antibiotic-refractory Lyme arthritis, where joint inflammation persists despite adequate antibiotic treatment. This is thought to be due to an ongoing autoimmune response rather than persistent infection. These patients may benefit from anti-inflammatory medications, disease-modifying antirheumatic drugs, or in some cases, synovectomy (surgical removal of the joint lining).

Post-Treatment Lyme Disease Syndrome

Some patients continue to experience symptoms such as fatigue, pain, and cognitive difficulties after completing antibiotic treatment. This condition is known as Post-Treatment Lyme Disease Syndrome (PTLDS). The cause is not fully understood – it may involve lingering immune responses, tissue damage from the initial infection, or other factors.

Importantly, multiple clinical trials have shown that additional prolonged courses of antibiotics do not improve outcomes for patients with PTLDS and can cause harm through antibiotic side effects. Treatment focuses on managing symptoms while allowing time for recovery, which usually occurs gradually over months.

How Can You Prevent Lyme Disease?

Prevent Lyme disease by avoiding tick bites: wear protective clothing in wooded areas, use EPA-registered tick repellents, perform daily tick checks, and remove attached ticks promptly and properly. Reducing tick habitat around your home and showering within 2 hours of being outdoors can also help.

Since there is currently no vaccine available for Lyme disease, prevention focuses on avoiding tick bites and promptly removing any ticks that do attach. A multi-layered approach combining personal protective measures, environmental management, and vigilant tick checks provides the best protection.

Personal Protective Measures

When spending time in areas where ticks are common – wooded areas, tall grass, leaf litter – take steps to minimize skin exposure to ticks. Wear long pants tucked into socks and long-sleeved shirts. Light-colored clothing makes ticks easier to spot, though some research suggests that dark clothing may attract fewer ticks in the first place.

Use EPA-registered tick repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. Products containing 20-30% DEET provide protection for several hours. For clothing and gear, permethrin-treated items are highly effective – permethrin kills ticks on contact and remains effective through several washings.

Stay on cleared trails when hiking, avoiding brushing against vegetation where ticks wait for hosts. Ticks don't jump or fly; they quest by holding onto vegetation with their lower legs while extending their upper legs to grab onto a passing host.

Tick Checks and Removal

Perhaps the most important prevention measure is performing thorough tick checks after spending time outdoors. Remember that nymphal ticks are very small – about the size of a poppy seed – and can easily be overlooked. Check these areas carefully:

• Under the arms and around the ears
• Inside the belly button and around the waist
• In and around the hairline and scalp
• Between the legs and behind the knees
• On pets that may bring ticks indoors

Showering within two hours of coming indoors has been shown to reduce the risk of Lyme disease, likely because it helps wash off unattached ticks and provides an opportunity for a tick check. Putting clothes in a hot dryer for 10 minutes kills ticks effectively – washing alone may not kill them.

Proper Tick Removal

If you find an attached tick, removing it correctly is important. Use fine-tipped tweezers to grasp the tick as close to the skin surface as possible. Pull upward with steady, even pressure – don't twist, jerk, or squeeze the tick's body. After removal, clean the bite area and your hands with rubbing alcohol or soap and water.

Avoid folk remedies like applying petroleum jelly, nail polish, or heat to make the tick detach. These methods don't work and may cause the tick to release more bacteria into the wound. The goal is to remove the tick as quickly and cleanly as possible.

Environmental Management

Reducing tick habitat around your home can decrease your risk of encountering ticks. Keep grass mowed short and remove leaf litter and brush. Create a barrier of wood chips or gravel between lawns and wooded areas. Keep playground equipment and outdoor sitting areas in sunny locations away from trees and shrubs.

Vaccines in Development

A Lyme disease vaccine called LYMErix was available from 1998 to 2002 but was withdrawn due to low sales and concerns about side effects. As of 2025, several new vaccines are in advanced clinical development. Valneva and Pfizer are developing a vaccine (VLA15) that has shown promising results in Phase 3 trials and may become available in the coming years.

What Are the Complications of Lyme Disease?

Without treatment, Lyme disease can cause serious complications including Lyme arthritis (chronic joint inflammation), neuroborreliosis (neurological problems like meningitis and facial palsy), Lyme carditis (heart rhythm abnormalities), and in rare cases in Europe, a chronic skin condition called acrodermatitis chronica atrophicans.

While most people who receive prompt treatment for Lyme disease recover completely, untreated or inadequately treated infections can lead to significant complications. Understanding these potential outcomes underscores the importance of early diagnosis and treatment.

Lyme Arthritis

Approximately 60% of patients with untreated Lyme disease develop Lyme arthritis, typically beginning months after the initial infection. The knee is the most commonly affected joint, though other large joints can be involved. The arthritis causes episodes of swelling and pain that can last weeks and may recur. In most cases, antibiotic treatment resolves the arthritis, but about 10% of patients develop antibiotic-refractory arthritis that may require additional interventions.

Neurological Complications

Neuroborreliosis can manifest as meningitis, cranial nerve palsies (most commonly facial palsy), radiculopathy (nerve root inflammation), or encephalitis. These complications are more common in children and in European Lyme disease. While most neurological symptoms resolve with antibiotic treatment, some patients may have persistent symptoms. Rarely, chronic neurological Lyme disease can cause cognitive difficulties, memory problems, and peripheral neuropathy.

Cardiac Complications

Lyme carditis occurs in about 1% of untreated Lyme disease cases and can cause varying degrees of heart block. While usually temporary and treatable, severe heart block can be life-threatening. There have been rare reported fatalities from Lyme carditis, typically in young adults who were not diagnosed in time.

Acrodermatitis Chronica Atrophicans

This late skin manifestation occurs primarily in European Lyme disease cases, caused by Borrelia afzelii. It begins with bluish-red discoloration and swelling of the skin, usually on the extremities, which over months to years becomes thin, atrophic, and wrinkled. Antibiotic treatment stops the progression but may not reverse existing skin changes.

Pregnancy Considerations

Lyme disease during pregnancy can be concerning, but there is no strong evidence that Borrelia infection causes congenital abnormalities when the mother receives appropriate antibiotic treatment. Untreated Lyme disease during pregnancy may theoretically pose risks, so prompt treatment is important. Doxycycline should be avoided during pregnancy, but amoxicillin and ceftriaxone are safe alternatives.