How many people get Lyme disease?

Each year, approximately 30,000 cases of Lyme disease are reported to CDC by state health departments and the District of Columbia. However, this number does not reflect every case of Lyme disease that occurs in the United States every year.

Surveillance systems provide vital information but they do not capture every illness. Because only a fraction of illnesses are reported, researchers need to estimate the total burden of illness to set public health goals, allocate resources, and measure the economic impact of disease. CDC uses the best data available and makes reasonable adjustments—based on related data, previous study results, and common assumptions—to account for shortcomings and missing pieces of information.

To improve public health, CDC wants to know how many people are actually diagnosed with Lyme disease each year and for this reason is conducting three complementary studies:

• Project 1 estimates the number of people diagnosed with Lyme disease based on medical claims information from a large insurance database.
• Project 2 estimates the number of people who test positive for Lyme disease based on data obtained from a survey of clinical laboratories.
• Project 3 uses survey data to estimate the number of people who report that they’ve been diagnosed with Lyme disease in the previous year.

Preliminary results from three different evaluation methods suggest that the number of people diagnosed with Lyme disease each year in the United States is around 300,000. Notably, this new estimate does not affect our understanding of the geographic distribution of Lyme disease. Most Lyme disease cases reported to CDC through national surveillance are concentrated heavily in the Northeast and upper Midwest, with 96 percent of reported cases occurring in 13 states. The preliminary results obtained using the new estimation methods mirror the geographic distribution of cases that is shown by national surveillance.

In August 2013, CDC scientists presented early results of these studies along with other scientists at the International Conference on Lyme Borreliosis in Boston, Mass. At the meeting, they described their different approaches (called research methods) and preliminary findings to other scientists. They will receive feedback and gain the insight of other scientists who are working on Lyme disease. This type of interaction is an important part of the scientific peer-review process. It makes science transparent and strengthens the quality of methods and findings that come from the methods. Finalized estimates will be published when these studies are complete.