Lyme Evidence Sheet
Reviewed 2026-07-24Why are reported Lyme cases different from estimated diagnoses?
Reported surveillance cases and estimated diagnoses answer different questions. Reported cases use surveillance definitions; estimates use methods designed to describe a broader burden of diagnosed illness.
What the evidence says
- CDC publishes aggregated surveillance data by geography and year.
- A CDC-supported analysis estimated the frequency of Lyme diagnoses using health-care data, rather than treating surveillance reports as all diagnoses.
What this can tell you
- Why two official-looking numbers can differ.
- Which question each source is designed to answer.
What this cannot tell you
- An individual’s personal risk.
- The exact number of infections in one place.
Sources (2)
- Centers for Disease Control and Prevention. ‘Lyme Disease Public Use Aggregated Data with Geography, 2022–2023.’ https://data.cdc.gov/National-Center-for-Emerging-and-Zoonotic-Infectio/Lyme-disease-public-use-aggregated-data-with-geogr/x5j9-wybp. Accessed July 24, 2026. Open source ↗
- Kugeler, K.J., et al. ‘Estimating the Frequency of Lyme Disease Diagnoses, United States, 2010–2018.’ Emerging Infectious Diseases, vol. 27, no. 2, 2021. https://wwwnc.cdc.gov/eid/article/27/2/20-2731_article. Open source ↗