Changes in Lyme disease surveillance may be behind the significant increases in recent reported case numbers, according to an article published in STAT. State representatives recently collaborated with the U.S. Centers for Disease Control and Prevention (CDC) to devise a new reporting strategy based on the Lyme disease caseload in each state. The new surveillance system—which was designed to alleviate the reporting burden on public health departments—requires only a positive blood test to report a case to the CDC in 15 states across the Northeastern, mid-Atlantic, and central Midwestern United States that have historically had the highest prevalence of Lyme disease. Other states must continue to collect clinical data on patients who test positive for Lyme disease. Health-care facilities in states that have had a high volume of Lyme disease cases, such as Massachusetts, have faced challenges investigating every case and following up with patients with other diseases. Using the new system, Massachusetts was able to report 5,052 cases in 2022, compared with the average of 144 cases per year between 2017 to 2019.
Experts stressed that the system may initially demonstrate concerning rises in case numbers. The CDC reported a 69% increase in cases in 2022—compared with the annual average of 37,118 cases between 2017 and 2019, there were 62,551 reported cases of Lyme disease in 2022. The experts suggested that the new system and subsequent 2022 statistics may further reflect that there may be far more cases of Lyme disease than have been historically reported. In the early stages of infection, current diagnostic tests cannot detect Lyme disease. Instead, they identify antibodies; however, it may be difficult to distinguish new antibodies from those developed in response to an older infection. As a result, physicians may make clinical diagnoses without performing a blood test. Estimates suggested that up to 476,000 cases of potential Lyme disease are treated each year, the majority of which are not reported to the CDC. “For Lyme disease, surveillance has always been imperfect. This [new system] continues to be imperfect, but it is a better, more sustainable way for states that have a high burden of this disease to be able to track trends in a way that allows us to compare those trends across state borders,” concluded Catherine Brown, DVM, MSc, MPH, President-Elect of the Council of State and Territorial Epidemiologists.