Are Cases of Lyme Disease Underreported in the US?


Lyme Disease is the most common vector-borne disease in the United States. Incidence rates have been increasing for years, and according to the CDC, there are approximately 20,000-30,000 reported cases of Lyme disease annually in the US alone.1

There are a number of reasons for the confirmed cases including increasing tick populations, expanding habitats, changing climate, reforestation, and better diagnostics.1

People contract Lyme disease through the bite of an infected blacklegged or western blacklegged tick, which are carriers of spirochete Borrelia (most commonly Borrelia burgdorferi in the United States).

A new study examined if there was potential underreporting of the disease. Specifically, The Veterans Health Administration (VA) performed an analysis examining their database.

"Automated case-finding was performed via ICD 9/10 Lyme Disease code plus a prescription for ≥7 days of appropriate antimicrobial treatment within 30 days of encounter AND/OR confirmatory lab testing,” the investigators wrote. “Data was extracted from VHA Corporate Data Warehouse. We calculated FY incidence and prevalence per 10,000 individuals in VHA care and analyzed demographic trends. Positive Predictive Value (PPV) of case-finding methodology and clinical characteristics of identified cases was determined by review of 75 randomly selected case records.”

Their findings did demonstrate an increase. “Automated methodology detected a total of 24,349 Lyme disease cases. Incidence rose steadily, peaking at 3.25 per 10,000 in FY 2017, with prevalence reaching 32.72/10,000 in FY 2022...Distribution of Lyme disease incidence expanded nationally, particularly in the Northeast and Northern Midwest. Demographic groups with highest average incidence per 10,000 in care included individuals in rural/highly rural areas (2.41), non-Hispanic Whites (2.26), age groups 55-64, 65-74, and 25-34 (2.30, 2.20, and 2.08, respectively), and males (1.95),” the investigators wrote.

The Department of Veterans Affairs presented findings on this study at IDWeek 2023.2

In conclusion, the investigators believed their methodology was able to capture accurate incidence numbers.

"Automated surveillance methodology for Lyme disease provided an efficient and reasonably accurate estimation of the epidemiology of Lyme disease in VHA. The VHA pattern of Lyme disease geographic expansion in recent years is consistent with CDC national reporting," the investigators wrote.

Although antibiotics can successfully treat the disease, biopharmaceutical companies are developing Lyme disease vaccines, and both Pfizer/Valneva and Moderna have investigational ones going through trials.

This article originally appeared on Contagion Live.

1. Division of Vector-Borne Diseases. CDC. Page last reviewed May 11, 2022. Accessed September 14, 2023.
2. Oda G, Lucero-Obusan C, et al. Two Decades of Lyme Disease in the U.S. Veterans Health Administration Detected Via Automated Surveillance Methodology, October 1999 - September 2022. Presented at: IDWeek 2023. October 11-14, 2023; Boston, MA. Abstract 1992.
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