A form of Lyme disease previously reported only in Minnesota and Wisconsin has been confirmed in a New York resident who had not traveled, and state scientists then found the bacterium in ten ticks collected from that person's property.
The finding was published by the CDC in the Morbidity and Mortality Weekly Report on June 4 and describes a case that began the previous summer. The New York State Department of Health was notified by a commercial laboratory on July 8, 2025, that a Herkimer County resident had tested positive for Borrelia mayonii. The patient, whose symptoms began in late June, was also infected with the bacterium that causes anaplasmosis, was treated with doxycycline and made a full recovery.
For households across the Northeast, the practical significance is not a new alarm. It is a reminder that the standard mental picture of Lyme disease, a single bull's-eye rash at the bite site, does not fit every infection blacklegged ticks carry. Adult tick activity picks up again in fall, which makes this a useful thing to know heading into hiking and yard cleanup season rather than a reason to change plans.
A Single Property in Herkimer County
After the case was reported, state investigators collected 147 blacklegged tick nymphs along hiking trails through the wooded property surrounding the patient's home and 22 more from a nearby forest. One Ixodes scapularis nymph tested positive using a newly validated real-time PCR assay. Investigators returned in late October, collected 305 adult ticks from the two locations, and detected nine more positive ticks from the patient's property, indicating local transmission rather than an imported infection.
The state then widened the search. In all, 1,518 ticks collected by standardized dragging surveys from 24 New York counties were screened. All ten positives came from that one Herkimer County property. Nothing turned up anywhere else. Surveys of that size can miss rare infections, so the result establishes that the bacterium is not widespread in the areas tested rather than proving it exists nowhere else in the state.
That containment is the most reassuring detail in the report and the one most often lost in summary coverage. The MMWR authors wrote that the work provides "the first evidence of B. mayonii presence in New York ticks" and locally acquired infection in a state resident. They also noted that the higher positivity rate among adult ticks compared with nymphs at the same site suggests an established local animal reservoir, such as mice or squirrels, rather than a one-time introduction by birds carrying infected ticks from the Midwest. Further characterization using next-generation sequencing will be needed to compare the New York samples with the original reference strain.
Borrelia mayonii was first identified as a cause of human illness in a Minnesota resident in 2013 and named as a distinct species and established as a cause of Lyme disease in 2016 by researchers at Mayo Clinic working with the CDC. It is carried by the same blacklegged tick that spreads Borrelia burgdorferi, the far more common cause of Lyme disease in the United States.
Symptoms That Do Not Match the Textbook Rash
The clinical differences are modest but worth knowing. According to the Minnesota Department of Health, commonly reported symptoms include fever or chills, headache, muscle or joint pain, and rash, with arthritis reported as a later-stage feature, much as it is with conventional Lyme disease.
Where the two diverge is the rash pattern. The CDC's summary of B. mayonii notes that unlike B. burgdorferi, this organism can also cause nausea and vomiting, large widespread rashes, and a higher concentration of bacteria in the blood.
Treatment does not change. Both bacteria respond to the same antibiotics, and the New York patient recovered after doxycycline. Diagnostic testing is the harder part, since the assay used in New York was newly developed and validated at the state's public health laboratory and is not part of routine commercial Lyme panels everywhere. Minnesota health officials advise clinicians to consult state public health staff when they suspect the infection, and the state's guidance for health professionals sets out the clinical picture and testing options.
Fall Tick Season and Reasonable Precautions
Nobody in New York needs to avoid the outdoors over ten ticks from one property. What is worth doing is what already reduces risk from every blacklegged tick pathogen in the region, including the common ones.
Use EPA-registered repellents on skin and permethrin on clothing and gear, and do not apply permethrin directly to skin. Stay toward the center of trails. Check for ticks after being outdoors, focusing on the scalp, ears, underarms, waistline, and behind the knees, and check children and pets too. Shower within a few hours and run clothing through a high-heat dryer cycle. Remove an attached tick promptly with fine-tipped tweezers, grasping close to the skin and pulling steadily upward. Prompt removal matters because a blacklegged tick generally must stay attached for 24 to 48 hours before it can transmit this bacterium.
Anyone who develops fever, chills, headache, muscle aches, or a rash within a month of possible tick exposure should tell a clinician about the exposure, whether or not a bite was noticed, and whether or not the rash looks like the classic target.
Several questions remain open. It is not known how B. mayonii reached Herkimer County or which local animal species is maintaining it. Whether it is established more widely in New York at levels too low for a survey of this size to detect has not been determined, and the sequencing results have not been published. New York's health department has said continued tick and human disease surveillance is what will answer those questions, and the CDC has not changed any national testing or treatment guidance based on this report.
Key Questions Answered
What was found in New York? The first locally acquired human infection with Borrelia mayonii in the state, plus ten positive blacklegged ticks from the patient's Herkimer County property.
When did this happen? The patient became ill in late June 2025 and was reported to the state on July 8, 2025. The CDC published the findings in MMWR on June 4.
Is this bacterium spreading across New York? Not based on current evidence. More than 1,500 ticks from 24 counties were tested, and every positive came from one property.
Is it more dangerous than ordinary Lyme disease? It can produce higher bacterial levels in the blood, more widespread rashes, and nausea and vomiting, but it responds to the same antibiotics.
Which rash should people watch for? Rashes with B. mayonii tend to be spread across the body rather than a single bull's-eye at the bite site, so an atypical rash should not be dismissed.
How is it treated? With the same antibiotics used for conventional Lyme disease. The New York patient received doxycycline and recovered fully.
What reduces the risk? EPA-registered repellents, permethrin-treated clothing, staying on trail centers, prompt tick checks and removal, showering after being outdoors, and high-heat drying of clothes.
