09/17/2026
Health officials have confirmed the first known case of a rare type of Lyme disease in New York, raising concerns that the bacterium may be expanding into new parts of the United States. Unlike the vast majority of Lyme disease cases, which are caused by *Borrelia burgdorferi*, this infection was caused by a much rarer relative called *Borrelia mayonii*. Until now, this bacterium had only been identified in Minnesota and Wisconsin. Investigators also found infected deer ticks on the patient's property, suggesting the bacterium may now be established locally.
Both forms of Lyme disease spread through bites from infected black-legged, or deer, ticks and respond to the same antibiotics when treated early. However, *Borrelia mayonii* can sometimes cause higher levels of bacteria in the bloodstream, more widespread skin rashes, nausea, vomiting, and illness severe enough to require hospitalization. After diagnosing the New York patient, researchers tested ticks from the surrounding area and detected the same bacterium in several of them, confirming local transmission.
Although this rare strain remains uncommon, the discovery highlights how tick-borne diseases can expand into new regions over time. Continued surveillance of ticks, wildlife, and human infections will help scientists track its spread, improve early diagnosis, and better understand how changing environments influence the movement of disease-causing bacteria.
RESEARCH PAPER 📄
DOI: 10.15585/mmwr.mm7521a2
