Lyme disease surveillance and available data
Lyme disease has been a nationally notifiable condition in the United States since 1991. Reports of Lyme disease are collected and verified by state and local health departments in accordance with their legal mandate and surveillance practices. After removal of personal identifiers, selected information on cases is shared with CDC through the National Notifiable Diseases Surveillance System (NNDSS). Policies regarding case definitions, reporting, confidentiality, and data release are determined by states and territories under the auspices of the Council of State and Territorial Epidemiologists (CSTE). Surveillance data have a number of limitations that need to be considered in the analysis, interpretation, and reporting of results. Additionally, answers to frequently asked questions related to surveillance are available.
Limitations of surveillance data
- Under-reporting and misclassification are features common to all surveillance systems. Not every case of Lyme disease is reported to CDC, and some cases that are reported may be due to another cause.
- Surveillance data are captured by county of residence, not county of exposure.
- States may close their annual surveillance dataset at a different time than CDC. Thus, the final case counts published by CDC may not exactly match numbers published by each state agency for a given year.
- Following its implementation in 1991, the national surveillance case definition for Lyme disease was modified in 1996, 2008, 2011, 2017, and again in 2022. Some of these changes impacted surveillance data and must be considered when attempting to interpret trends. Case definitions for each period are available.
Publicly available surveillance data
- Final annual case counts are published when the year is over and all states and territories have verified their data, typically in the fall of the following year. Data through 2015 can be found in the MMWR Summary of Notifiable Diseases. Data from 2016 forward are found in CDC WONDER.
- Selected Lyme disease statistics, tables and charts are available on the CDC Lyme disease website.
- To facilitate the public health and research community’s access to NNDSS data on Lyme disease, CDC has developed several public use datasets.