Lyme disease is an infectious condition spread through the bite of certain ticks. It frequently causes fatigue and headache and can progress to arthritis and other complications. 

Lyme disease affects about eight out of every 100,000 Americans annually, according to the Centers for Disease Control and Prevention (CDC). It is the leading tick-borne disease in North America and Europe. In the United States, it is most common in the Northeast and parts of the Midwest, but in a typical year it occurs in all but a few states.

In addition to fatigue and headache, indicators of Lyme disease can include fever, joint pain and a red rash. Symptoms vary according to the disease's level of advancement.

Lyme disease is often difficult to diagnose. Symptoms may mimic those of other conditions. As a result, several types of testing, such as blood tests and in some cases a spinal tap, may be performed.

Depending on the phase of infection, oral or intravenous antibiotics are administered. Lyme disease may be successfully treated at any stage, though treatment is most effective when diagnosis comes early. Occasionally, post-Lyme disease syndrome can occur when symptoms persist long after treatment or eradication has ended.

Left untreated, Lyme disease can cause complications such as meningitis, encephalitis, partial paralysis, cognitive defects or heart problems. In rare cases it can be fatal. In addition, patients with Lyme disease may be infected with two other potentially serious diseases transmitted by the same tick: human granulocytic anaplasmosis (HGA) and babesiosis.

A vaccine was once available to help prevent people from getting Lyme disease. However, its sale was discontinued in 2002 amid concerns of significant complications in some users. Preventive measures remain the most effective methods of reducing exposure. These steps include using repellant with DEET, wearing proper clothing and inspecting the skin for ticks.

Lyme disease is a multi-system infectious condition that frequently causes fatigue and headache and can progress to arthritis, memory problems and other complications. It is the leading tick-borne disease in the United States.

Lyme disease occurs most often in rural and suburban areas in the U.S. Northeast, mid-Atlantic region and upper Midwest. It also affects parts of Canada, Europe, Australia and Asia, where it is often called Lyme borreliosis. Lyme disease was first identified in the United States in 1975 near Lyme, Conn. However, its existence has been documented in Europe for almost a century.

Lyme disease progresses in three stages: early localized, early disseminated and late Lyme disease. As the bacteria spread, symptoms of fatigue and headache may appear.

If the disease progresses to late Lyme disease, arthritic symptoms can appear, along with cognitive difficulties and skin puffiness. These may take months or years to appear.

When treated, most people recover quickly and experience very few complications from Lyme disease. A small percentage of patients recover slowly or do not fully recover from symptoms if they are not treated in a timely manner.

According to the U.S. Centers for Disease Control and Prevention (CDC), 19,931 cases of Lyme disease were reported from 46 states and the District of Columbia in 2006. The incidence has generally risen since 1991, when fewer than 10,000 cases were reported, but might have peaked in 2002. The vast majority of U.S. cases occur in the region stretching from Maine to Virginia and in Minnesota and Wisconsin. Parts of northern California, Iowa, Michigan and northern Illinois also have increased risk. The agency considers the Southeast and southern Midwest to be low-risk areas.

About eight cases for every 100,000 Americans were reported in 2006, according to the CDC. In the 10 states where Lyme disease is most common, there were about 30 cases for every 100,000 people.

Bacteria called Borrelia burgdorferi cause Lyme disease. These bacteria are transmitted to humans through bites from infected ixodes ticks, which may be referred to as deer ticks or black-legged ticks in the eastern United States and western black-legged ticks in the western United States. These tiny ticks are smaller than those typically found on a dog and are difficult to spot.

The disease spreads when an infected tick takes a blood meal, passing infectious bacteria to an animal (usually a deer or mouse, sometimes another mammal or a bird) and making them a host for the disease. Other ticks feeding on the infected host animal contract the disease themselves, then pass it to more deer or mice. Ticks await new hosts by hiding within areas dense with grass or shrubs, most notably those along boundaries between residential properties and surrounding forest land and along deer paths. A tick senses carbon dioxide exhaled by humans or animals as they pass. The tick attaches itself to body parts that happen to rub up against it.

The tick must remain affixed to human skin for at least 36 hours for humans to become infected.  Furthermore, the tick can take as long as 24 hours from the time it attaches itself before feeding may even begin.  As a result, Lyme disease affects very few people who are bitten, even in areas with high populations of infected ticks. 

Lyme disease is most common in the summer and early fall when biting ticks are young, small and difficult to detect. Less frequent are cases in the late fall, early winter and early spring when biting ticks are fully developed and easier to spot.

The ticks that transmit Lyme disease can also spread two other conditions: human granulocytic anaplasmosis (HGA) and babesiosis. Infection with HGA (formerly known as ehrlichiosis) may be widespread but unrecognized, according to the CDC. Symptoms include malaise, fever, muscle pain (myalgia) and headache. In rare cases death has resulted.

Babesiosis is an infection of the red blood cells by a tiny parasitic protozoan. It can cause anemia and a malaria-like illness marked by fever, chills, excessive perspiration, muscle pain, headache and malaise. Patients infected with both diseases are more likely than those afflicted only with Lyme disease to experience symptoms including fatigue, anorexia (loss of appetite), unstable emotions, nausea, conjunctivitis (an inflammation of the eye) and splenomegaly (enlarged spleen), according to the National Institutes of Health (NIH). In rare cases death has resulted. Babesiosis may affect about 10 percent of Lyme disease patients in southern New England, according to the NIH.

As with Lyme disease, HGA and babesiosis are treated with antibiotics and respond best to early treatment.

Lyme disease is an infectious condition transmitted to humans through bites from infected deer ticks. Children and young adults living in areas where ticks are more common, such as wooded areas, have the highest risk of contracting Lyme disease, although anyone can be infected. Individuals previously diagnosed with Lyme disease can acquire it again if bitten by another infected tick.

Common risk factors for Lyme disease include:

• Spending time in wooded areas. In the United States, deer ticks are most abundant in heavily wooded areas of the Northeast, Mid-Atlantic region and upper Midwest.  Spending significant amounts of time outdoors in these locations during warmer times of the year increases one’s risk for exposure to Lyme disease.
  
  
• Exposed skin. Ticks attach themselves to uncovered skin. Exposing arms and legs while outdoors in areas with high tick populations increases the chance of getting bitten by an infected tick.
  
  
• Improper or delayed removal of ticks. Removing ticks within 24 to 48 hours of attachment substantially lowers the risk of acquiring Lyme disease.

A variety of signs and symptoms are associated with Lyme disease (an infection caused by a deer tick's bite). Some are specific only to Lyme disease itself, and others are similar to symptoms of different medical conditions. Accordingly, the signs and symptoms may differ depending on the stage of the disease. Lyme disease generally progresses in three stages:

• Early localized Lyme disease. This is distinguished by elevated red skin lesions called erythema migrans (EM) at the site of the tick bite, which is typically at the underarm, groin, back of the knees or waist. As bacteria spread in the bloodstream, so does the rash. Its appearance is made up of multiple rings, similar in appearance to a "bull's-eye."
  
  Almost all people with Lyme disease develop this symptom, even if they do not recall being bitten by a tick. EM usually appears within a window of about one week and lasts for several days. However, it can take as long as one month to appear and last for several weeks in some instances.
  
  Flu-like symptoms (e.g., fatigue, headache, muscle and joint pain, swollen lymph nodes) may also be present during early localized Lyme disease.
  
  
• Early disseminated Lyme disease. During this stage, the bloodstream spreads the bacteria to other areas of the body, sometimes inflaming tissues. Often the symptoms exhibited by people with this stage of Lyme disease are the first to be reported. Symptoms of early disseminated Lyme disease include:
  
• • Heart inflammation. People with untreated early disseminated Lyme disease may experience this or other related cardiac symptoms (e.g., pericarditis, heart block) although the occurrence is relatively uncommon.
    
    
  • Neurologic disorders. In rare cases, inflammation in the central nervous system may cause meningitis (inflammation of the tissue covering the brain and spinal cord) or encephalitis (inflammation of the brain) in people with early disseminated Lyme disease. These symptoms may be characterized by headache or a stiff neck. Other problems may also occur, such as numbness or weakness in limbs, peripheral neuropathy, partial paralysis, facial nerve palsy (Bell's palsy) or odd sensations.
    
    
• Late Lyme disease. Symptoms of late Lyme disease may not be apparent for several months or years after being bitten by an infected tick. However, these may be the first symptoms of the disease for some individuals, and may include:
  
• • Joint or muscle pain. This is common in people with late Lyme disease who have not been treated. Intermittent and sometimes chronic episodes of asymmetric arthritis (joint inflammation) occur frequently in people with this stage of the disease. Sometimes arthritis has also been seen in early stages.
    
    
  • Neurologic symptoms. A variety of neurologic symptoms (e.g., pain, impaired memory or judgment, odd sensations or numbness, temporary paralysis) can occur during late Lyme disease.
    
    
  • Skin symptoms. European Lyme disease (Lyme borreliosis) in its late phase may cause certain skin problems (e.g., lumps, patchiness, puffiness) on parts of the hands, feet, knees or elbows.

After Lyme disease has been successfully treated and eradicated, vague symptoms (e.g., headache, fatigue, joint pain) may persist. Collectively, this phenomenon is known as post-Lyme disease syndrome. Fibromyalgia, a chronic pain disorder, is common in people who experience post-Lyme syndrome, although why this occurs is not fully clear.

Diagnosis of Lyme disease begins with a medical history, including questions about exposure to deer ticks, and a physical examination, including inspection of the skin for the red rash known as erythema migrans (EM).  

However, this disease is often difficult to diagnose. Its symptoms can be confused with indicators of other conditions, such as fibromyalgia or chronic fatigue syndrome. Also, some people in an endemic (infected) area may have the disease without the rash or other signs and symptoms. Usually the patient has a lot of testing before Lyme disease is diagnosed.

Consequently, several tests may be used in diagnosis, such as:

• Enzyme-linked immunosorbent assay (ELISA) test. Antibodies that fight Lyme disease bacteria are measured using the ELISA blood test. These antibodies take time to develop. As a result, many people with early localized Lyme disease have a negative ELISA test result. Furthermore, some individuals who do not have Lyme disease falsely test positive because of similarities between Borrelia burgdorferi (the bacteria that cause Lyme disease) and other organisms normally found in the body.
  
  
• Western blot test. This blood test is used to either prove or disprove ELISA test results when they are either positive or inconclusive. Western blot test is also useful in determining when an ELISA test is falsely positive.
  
  
• Spinal tap (lumbar puncture). A needle inserted through the lower back withdraws a sample of cerebrospinal fluid (the fluid surrounding the brain and spinal cord) for laboratory analysis. The procedure may be used if meningitis or encephalitis is suspected.   
  
  
• Imaging. CAT scan (computed axial tomography) or MRI (magnetic resonance imaging) of the brain may be performed to rule out the presence of other conditions with symptoms similar to Lyme disease. An electrocardiogram (ECG or EKG) may be performed if possible heart complications are present.  

• Skin biopsy. Rarely, a sample of skin tissue may be taken and analyzed to identify the bacteria.

The presence of erythema migrans is important in diagnosis of Lyme disease. Unlike many other types of infections, blood tests for Lyme disease are sometimes falsely positive (inaccurately indicating the disease where it is not present) when there are only nonspecific symptoms. In an attempt to avoid unnecessary treatment, blood tests are rarely performed when EM is not present.

Any stage of Lyme disease is treatable in almost all circumstances. Most people experience a full, quick recovery with minor complications. However, some people recover slowly if diagnosed when the disease is in its later stages.  Left untreated, Lyme disease can be permanently disabling or even fatal in some instances.

Lyme disease can be treated most effectively with minimal risk for further complications if diagnosed in its early stages. Antibiotics stop the disease from progressing and may lessen the severity of symptoms. Patients experiencing early-phase Lyme disease receive oral antibiotics daily for 10 to 14 days. In certain cases oral antibiotics may produce side effects such as upset stomach, diarrhea or allergic reaction.

Arthritis that is caused by Lyme disease (infectious arthritis) is also treated with antibiotic therapy. In some cases when arthritis lingers after antibiotic treatment, drugs that suppress inflammation may be required.

Late-stage, ongoing or serious Lyme disease usually requires intravenous (I.V.) antibiotics (e.g., ceftriaxone, cefotaxime). Through a catheter placed in a vein, antibiotics are administered daily for about two to four weeks. Side effects of I.V. antibiotics vary and may include a decrease in white blood cells, abdominal pain, diarrhea, colitis (inflammation of the colon) or allergic reaction.

People with Lyme disease may also need anti-inflammatory medication such as ibuprofen to reduce inflammation and pain and to improve function.

Patients receiving antibiotic treatment for Lyme disease sometimes experience a short–term worsening of symptoms (Jarisch-Herxheimer reaction) caused by dying bacteria. It typically begins about 24 hours after antibiotic treatment has begun and lasts about the same amount of time before ending. Antibiotics should continue to be administered as originally intended if a Jarisch-Herxheimer reaction occurs.  

In cases where antibiotic treatment shows no effect in an individual considered to have Lyme disease, re-evaluation by a physician is typically necessary. The most common reason for this occurrence is misdiagnosis, with symptoms attributed to Lyme disease actually being caused by another condition.

Patients are urged not to try unproven, unapproved and possibly dangerous substances that are sometimes touted as a cure for Lyme disease. The U.S. Food and Drug Administration in 2006 issued a warning against an injected compound called bismacine or chromacine. It can cause complications including kidney failure and cardiovascular collapse and is blamed for at least one death.

The Infectious Diseases Society of America (IDSA) updated its guidelines on Lyme disease in 2006. Its general recommendations include:

• Not routinely using antibiotics after a tick bite
  
  
• Offering one oral dose of the antibiotic doxycycline only in specific circumstances for people who were bitten by a tick but do not show symptoms of the disease
  
  
• Treating early Lyme disease with oral doxycycline, amoxicillin or cefuroxime axetil
  
  
• Avoiding doxycycline in pregnant patients
  
  
• Treating early neurologic Lyme disease (involving meningitis or radiculopathy) with intravenous ceftriaxone
  
  
• Treating late neurologic Lyme disease with intravenous ceftriaxone or, as an alternative, intravenous cefotaxime or penicillin G
  
  
• Not using certain treatments described as lacking in scientific evidence, such as hyperbaric (high-pressure) oxygen, ozone, fever therapy, certain dietary supplements, long-term use of antibiotics, combinations of antimicrobials, pulsed dosing, first-generation cephalosporins, fluoroquinolones, carbapenems, vancomycin, metronidazole, tinidazole, amantadine, ketolides, isoniazid, trimethoprim-sulfamethoxazole, fluconazole or benzathine penicillin G
  
  
• Using antimicrobials to treat the other diseases spread by the Lyme disease tick: human granulocytic anaplasmosis (HGA) and babesiosis. Doxycycline is suggested for all symptomatic patients suspected of having HGA. A combination of atovaquone and azithromycin, or clindamycin and quinine, is suggested for patients with active babesiosis.

The guidelines emphasize that they do not apply in all cases and are not meant to replace a physician's recommendations. They also stress the importance of preventing Lyme disease by reducing exposure to ticks.

The IDSA's recommendations have sparked some controversy, including criticism from the Lyme Disease Association that the opposition to long-term antibiotic therapy was depriving chronic Lyme patients of beneficial treatment. The International Lyme and Associated Disease Society (ILADS) recommends that antibiotic treatment be guided by the patient's response rather than preset limits, and says that for persistent Lyme disease a patient may need to be treated for months after symptoms have disappeared.

A vaccine for preventing Lyme disease was once available. However, it was removed from the market in 2002 by the manufacturer amid concerns of serious side effects (e.g., arthritis, neurological problems) in some patients.  Other vaccines are being studied, although none are available for the prevention of Lyme disease. Consequently, personal and environmental precautions are necessary to reduce the chance of exposure, including: 

• Habitually inspecting the skin for ticks. It is also important to check children after they spend time outdoors.
  
  
• Removing ticks promptly and properly once spotted. Using tweezers, grab hold of the tick as close to the skin as possible. Pull back evenly without squeezing or jerking while removing the tick. Follow by disinfecting hands and skin after the tick has been removed.
  
  
• Knowing which outdoor locations pose the biggest threat (e.g., heavily wooded areas).
  
  
• Covering the skin in areas with high tick populations. Wearing proper clothing (e.g., long-sleeved shirts, long pants tucked into socks or gaiters) helps ward off ticks.
  
  
• Using tick repellants. The U.S. Centers for Disease Control and Prevention (CDC) suggests taking more precautions in May, June and July, and applying DEET-containing repellant to clothes and exposed skin and permethrin to clothes. Certain people (e.g., young children, pregnant or breastfeeding women) may not be able to use DEET.
  
  
• Not letting pet roams free. In addition, dogs, cats and horses should be inspected for ticks after going for a walk, especially in wooded or overgrown areas. Lyme disease has also been diagnosed in goats and cattle, and other species might also be vulnerable, according to the Lyme Disease Foundation.
  
  
• Installing a tall fence. Because deer carry ticks and often host Lyme disease, building a high fence may reduce the possibility of contracting Lyme disease.
  
  
• Keeping lawns trimmed. Regular lawn maintenance increases exposure to the sun, thereby discouraging ticks from residing in the grass.
  
  
• Laying wood chips. Putting down mulch along the perimeter of a property can discourage ticks from traveling out of wooded areas to a person’s lawn.
  
  
• Treating structures. Certain treatments can kill ticks and mice (their hosts) and reduce exposure when applied to stone walls and areas bordering forests.  

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about Lyme disease:

1. Do I live in an area at high risk for Lyme disease?
   
   
2. Should I use an insect repellant with DEET? Is it safe for my children or not?
   
   
3. What tick repellants are safest for my children or for me if I am pregnant?
   
   
4. How concerned should I be about contracting Lyme disease?
   
   
5. How can I tell the difference between ordinary skin irritation and erythema migrans?
   
   
6. Do my symptoms suggest I may have Lyme disease?
   
   

7. What other conditions could be causing my symptoms?
   

8. What diagnostic tests for Lyme disease might I undergo?
   

9. How long should it take me to recover from Lyme disease?
   

10. What will be done if my Lyme disease doesn't clear up like most cases do?
    

11. I'm confused about the conflicting recommendations on treating chronic Lyme disease -- for how long may antibiotics be taken?
    

12. Are any vaccines for Lyme disease close to being put on the market? If so, should I be vaccinated?