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Lyme Disease Cases Much Higher Than Thought, Studies Suggest

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September 11, 2013

The Centers for Disease Control and Prevention (CDC) has released preliminary new data on the number of people in the United States who are diagnosed with Lyme disease each year. The new estimate is 300,000 cases annually, not the 30,000 previously thought.

The larger estimate, based on data from three ongoing studies, was presented last month at the 2013 International Conference on Lyme Borreliosis and Other Tick-Borne Diseases. According to the CDC, the higher estimate supports studies that go back as far as the 1990s showing that the actual number of Lyme disease cases is 3 to 12 times higher than the number of cases that are reported each year.

As stated by Paul Mead, MD, MPH, chief of epidemiology and surveillance for CDC's Lyme disease program in the CDC's August 19th press release, "We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater. This new preliminary estimate confirms that Lyme disease is a tremendous public health problem in the United States, and clearly highlights the urgent need for prevention."

The new, higher estimate does not mean that many Lyme disease cases go untreated, says the CDC, only that they may go unreported to state and federal public health laboratories. However, low disease estimates from under-reporting can create an inaccurate picture of the scope of a public health problem such as this—especially when the incidence may be so much higher than previously thought. Better estimates can help increase awareness of the issue, providing additional incentive for the general public, government, and medical community to focus on this disease and its prevention.

Lyme disease is an infection caused by Borrelia burgdorferi bacteria, which are carried by blacklegged ticks. It is most common in the Midwest and Northeast U.S. Thirteen states account for 96% of cases (see CDC's Lyme Disease Map). Infections generally occur in the spring and summer when ticks are most active and people spend more time outdoors. Not all tick bites cause Lyme disease, however, because not every tick is infected with the bacterium and it takes a tick from 24 to 72 hours to infect a person after attaching itself.

The first symptom of Lyme disease is usually a bull's-eye rash that appears a few days to a month after the tick bite in up to 75% of those infected. Progression of the infection can lead to other symptoms, such as headache, fatigue, fever and chills. More severe symptoms of untreated Lyme disease can include muscle and joint pain, facial weakness and paralysis, numbness and pain in the arms and legs, meningitis, blurred vision and trouble concentrating. People diagnosed at a later stage of Lyme disease may have persistent symptoms and are considered to have Post-treatment Lyme disease syndrome (PTLDS).

It is important to understand that Lyme disease can sometimes be challenging to diagnose. A health practitioner may base a diagnosis on a patient's symptoms and history of tick bite or exposure to an area with a high prevalence of Lyme disease. However, not everyone infected with Lyme disease develops the bull's-eye rash or notices other more nonspecific symptoms. Laboratory testing for people who do not have symptoms is not recommended by the CDC because it contributes to a high rate of false positives. False positives on antibody tests for Lyme disease can also be caused by infections with other bacteria that are similar to B. burgdorferi, such as the one that causes syphilis. Therefore, positive or indeterminate test results should always be confirmed using another method. False negatives can occur if testing is performed too soon, before the body has had time to produce antibodies to B. burgdorferi, which can take several weeks.

The CDC continues to analyze the data from the three studies prior to their completion. Individuals, especially those in states with high rates of Lyme disease, can protect themselves by following steps recommended by the CDC, such as using repellent to ward off ticks, checking frequently for ticks and removing any attached ones quickly and correctly, and being aware of the symptoms of Lyme disease. If you experience any symptoms, such as rash or fever, and have been in an area known to have infected ticks, consult your health care provider.

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Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used. To access online sources, copy and paste the URL into your browser.

Centers for Disease Control and Prevention. Press Release: CDC provides estimate of Americans diagnosed with Lyme disease each year. Monday, August 19, 2013. Available online at through Accessed September 3, 2013.

Centers for Disease Control and Prevention. Lyme disease transmission. Available online at through Accessed September 3, 2013.

Centers for Disease Control and Prevention. Signs and Symptoms of Lyme Disease. Available online at through Accessed September 3, 2013.

Centers for Disease Control and Prevention. Lyme Disease Diagnosis and Testing. Available online at through Accessed September 3, 2013.

Centers for Disease Control and Prevention. Preventing Tick Bites. Available online at through Accessed September 3, 2013.

Stobbe, Mike. Associated Press. New Lyme disease estimate: 300,000 cases a year. Monday, August 19, 2013. Available online at through Accessed September 2013.

HealthDay News. U.S. Lyme Disease Cases Vastly Underreported: CDC Ongoing studies suggest ticks infect 300,000 people each year. Monday, August 19, 2013. Available online at through Accessed September 2013.