Key points
- CDC monitors Lyme disease through national case surveillance and other data sources.
- More than 80,000 Lyme disease cases are reported to CDC each year.
- An estimate using insurance claims suggests 476,000 people are treated for Lyme disease each year.
Surveillance data explained
More than 80,000 Lyme disease cases are reported to CDC each year by states and jurisdictions.
Lyme disease became a nationally notifiable condition in the United States in 1991. Case reports of Lyme disease are routinely collected and verified by state and local health departments in accordance with their legal mandate and surveillance practices. Cases are then classified according to the national surveillance case definition developed by the Council of State and Territorial Epidemiologists (CSTE).
After information that could identify a person is removed, selected case information is shared with CDC through the National Notifiable Diseases Surveillance System (NNDSS). CDC provides surveillance data to the public in a variety of formats in accordance with current data release standards that protect patient privacy.
Lyme disease surveillance data have some limitations that need to be considered in the analysis, interpretation, and reporting of results.
- Underreporting and misclassification can occur in all disease surveillance systems. Lyme disease surveillance does not capture every case, and some cases reported through surveillance may have another cause.
- Surveillance data are collected and reported based on where people live, not where they got Lyme disease.
- States sometimes finalize their yearly surveillance data at different times than CDC, so case counts published by CDC may differ slightly from those reported by individual states for the same year.
- The national case definition for Lyme disease has changed several times since national surveillance began in 1991, including in 1996, 2008, 2011, 2017, and 2022. Some of these changes affected how cases were counted and should be considered when looking at trends over time.
Other data sources
In addition to national surveillance data, CDC uses other sources of information to monitor trends related to Lyme disease.
- Insurance claims data show changes in the number of Lyme disease diagnoses over time. An estimate based on these data suggests 476,000 people may be diagnosed and treated for Lyme disease each year in the United States. This may be an overestimate because billing codes do not always reflect a confirmed Lyme disease diagnosis.
- CDC established the Surveillance Based Lyme Disease Network (SubLyme) in 2023 to strengthen Lyme disease surveillance and research using electronic health record (EHR) data. CDC partners with large healthcare systems in areas where Lyme disease is common, including Maine, Massachusetts, Pennsylvania, and Wisconsin.
- The Tick Bite Data Tracker shares emergency department data on visits for tick bites by week, geographic region, and patient age and sex. These data can be used to inform people in different parts of the country when their risk for tick bites may be increasing. The tracker uses data reported to the National Syndromic Surveillance Program (NSSP).
- CDC collects data to track where blacklegged and western blacklegged ticks are found and where they are infected with the bacteria that causes Lyme disease. These data are used to inform public health guidance for people and healthcare providers.
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