Rates of Babesiosis Infection Increasing in Both Endemic, Non-Endemic States

February 24, 2021

Rates of babesiosis infections grew among Medicare beneficiaries in states where Babesia microti is endemic, according to findings from a retrospective study of the Medicare claims database. Rates of babesiosis also increased by several times in states previously considered non-endemic, suggesting that the geographic range of babesiosis has expanded. The study is a collaboration between the Food and Drug Administration, the Centers for Medicare and Medicaid Services and Acumen LLC. Investigators published their findings in the February issue of Open Forum Infectious Diseases.

Between 2006 and 2017, 19,469 Medicare beneficiaries nationwide had a recorded babesiosis diagnosis, an overall national rate of 6 per 100,000 person-years. This rate increased from 4 per 100,000 person-years in 2006 to 9 per 100,000 person-years in 2017. By state, the highest babesiosis rates (per 100,000 person-years) were in the endemic states of Massachusetts (62), Rhode Island (61), Connecticut (51), New York (30) and New Jersey (19). Among all seven endemic states, the rate increased from 17 in 2006 to 42 in 2017.

Furthermore, the study identified substantially increasing babesiosis trends in the non-endemic states of Maine (11), New Hampshire (12) and Vermont (10), which had rates comparable to the well-established states. Pennsylvania (5) and Delaware (4) also had markedly increasing babesiosis trends, with the latest rates comparable to or higher than those for the endemic states of Minnesota (5) and Wisconsin (4). According to the authors, the increase in recorded babesiosis diagnoses over time suggests a need to monitor babesiosis distribution patterns in all states to help better understand local and travel-associated transmissions.

The study also identified high-risk counties, which the authors believe can support the development and implementation of appropriate prevention strategies by public health organizations at the national, state and local levels. Furthermore, the authors believe that the study emphasizes the utility of real-world evidence as a tool for better understanding, monitoring and tracking national, regional, local, seasonal and other babesiosis transmission patterns in support of public health efforts.