Rare Lyme Disease-Causing Strain Spreads to New State: What to Know
Rare Lyme disease causing strain spreads – A previously uncommon pathogen linked to Lyme disease has recently been identified in a state outside its typical range, according to a report from the Centers for Disease Control and Prevention. This discovery marks a significant shift in the geographic spread of the disease, which has historically been concentrated in specific regions of the United States.
The Prevalence of Lyme Disease
Lyme disease, a tick-borne illness, is not a rare occurrence. In 2023 alone, over 89,000 cases were reported to the CDC, with health officials estimating the actual number of annual diagnoses could be as high as 476,000. This highlights the growing public health concern surrounding the disease, despite its traditional distribution patterns.
While nearly every state in the U.S. had at least one reported case of Lyme disease in 2023, the majority of infections were traced to Wisconsin, Minnesota, and the Northeastern region. A recent CDC map illustrates this trend, showing that these areas accounted for the bulk of cases, though the disease’s presence is now expanding into new territories.
How the Disease Spreads
Lyme disease is primarily transmitted through the bite of the blacklegged tick, also known as the deer tick or Ixodes scapularis. The Cleveland Clinic explains that symptoms often begin with a distinctive “bullseye” rash, followed by fever, chills, and headaches. In more advanced stages, the infection can lead to complications affecting the nervous system, heart, and joints.
“The disease is typically caused by the bacterium Borrelia burgdorferi,” the CDC notes. “However, in rare instances, another species, Borrelia mayonii, may also be responsible for cases.”
Borrelia mayonii is classified as a “rare, newly emerging species” by Wisconsin health officials. The strain was first confirmed to cause human illness in a Minnesota resident in 2021, three years after its initial identification in the state. Since then, it has been detected in 10 cases across Wisconsin, with symptoms overlapping those caused by Borrelia burgdorferi, including fever, chills, headache, rash, and joint pain. Arthritis, however, is more commonly reported in later-stage infections.
A New Frontier for B. mayonii
The spread of B. mayonii has now extended beyond Wisconsin and Minnesota, as a 2025 CDC report reveals. For the first time, the strain was found in Herkimer County, New York, where a local resident tested positive for the bacteria. The report, released earlier this month, explained that a nymph stage of the blacklegged tick (Ixodes scapularis) collected from the individual’s property was confirmed to carry the pathogen. Additionally, nine more ticks from the same area were found to be positive.
This marks the first documented case of B. mayonii in New York, raising questions about how the strain might have reached the region. The CDC emphasizes the importance of ongoing monitoring, stating that the emergence of this pathogen in new locations underscores the need for vigilance. “Continued surveillance of tick-borne disease is critical,” the report authors add, noting that the strain’s spread could have broader implications for public health.
According to the New York State Department of Health, the proportion of ticks testing positive for B. mayonii remains relatively low. Of 627 nymph ticks examined, only one showed infection, while nine adults out of 891 were positive. On the patient’s property, the infection rate was higher, with 0.7% of nymphs and 3.9% of adults carrying the bacteria. These findings suggest that while the strain is rare, its presence in new areas warrants closer attention.
The Geographic Reach of Blacklegged Ticks
CDC data reveals that the blacklegged tick (Ixodes scapularis) is now found in more than half of the U.S. states, stretching from North Dakota south to Texas, east to Florida, and back north to Maine. This widespread distribution means that Lyme disease and its associated strains pose a risk in regions that may have previously considered themselves less vulnerable.
Experts warn that the blacklegged tick can transmit a variety of illnesses beyond Lyme disease. In addition to B. burgdorferi and B. mayonii, the tick is also linked to anaplasmosis, babesiosis, hard tick relapsing fever, ehrlichiosis, and the Powassan virus. These co-infections highlight the complexity of tick-borne diseases and the importance of comprehensive testing and reporting.
The detection of B. mayonii in New York signals a potential expansion of its geographic footprint. While the strain is not yet widespread, its presence in the Northeast raises the possibility of further spread. Health officials are now working to understand how the pathogen might have traveled and whether it could become more common in the region.
As the blacklegged tick continues to thrive across diverse climates, the risk of Lyme disease and its emerging variants is likely to grow. The CDC’s findings in New York serve as a reminder that the disease’s reach is evolving, requiring updated strategies for prevention and treatment. With more than 89,000 cases reported in 2023, the need for ongoing research and public awareness has never been greater.
Implications for Public Health
The spread of B. mayonii to New York underscores the dynamic nature of tick-borne illnesses. While the majority of Lyme disease cases are still attributed to B. burgdorferi, the emergence of this new strain adds another layer to the disease’s complexity. Health experts caution that increased surveillance and rapid response efforts will be key to mitigating its impact.
For residents in areas where the blacklegged tick is active, awareness of the different strains and their symptoms is essential. Early detection and treatment can prevent the progression of Lyme disease, reducing the risk of long-term complications. As the CDC continues to track the spread of B. mayonii, it is likely to become a more prominent focus in the coming years.
With the strain now appearing in New York, the potential for Lyme disease to spread further is a growing concern. The CDC’s report on the discovery serves as both a warning and a call to action for health departments, researchers, and communities to prepare for this new development. As the blacklegged tick population expands and the climate changes, the fight against Lyme disease and its rare variants is entering a new phase.
