Stony Brook Medicine researchers have identified the first Bourbon virus case in New York, a diagnosis they say came in April 2026 after a patient was hospitalized with severe symptoms. Luis Marcos said the patient was first treated for Lyme disease with doxycycline, but the drug did not help.
The finding adds a New York case to a virus that has already turned up in Kansas, Missouri, the Midwest, the East Coast and the Southern US. Marcos said the case fits a problem doctors may face more often: Bourbon virus can look like other tick-borne illnesses before laboratory testing points in its direction.
Luis Marcos on the New York case
Marcos, the lead author of the study and director of Stony Brook University’s Tick-Borne Diseases Clinic, said the patient was the Bourbon virus case and that antibody titers rose eight-fold over a one-month period. “This one case certainly was the Bourbon virus, and over a one-month period antibody titers increased eight-fold. The patient had showed some very severe symptoms and was hospitalised,” he said.
The study drew on 107 individuals with tick-borne illness symptoms between 2019 and 2024. Blood samples analyzed at the New York State Department of Health found two cases with neutralising antibodies for Bourbon virus, and one showed a four-fold rise in neutralising antibodies, which the researchers said pointed to a severe or very recent infection.
Why diagnosis is difficult
Marcos said the virus is easy to miss because the symptoms resemble other tick-borne infections and because there is no commercial test, vaccine or targeted treatment. He said, “There are a lot of lone star ticks in New York and in the Northeast, we have dense populations, and when someone is infected with Bourbon virus, symptoms are similar to other tick-borne infections,” and added, “For these reasons, the Bourbon virus is likely more prevalent than we think in our region and other cases are likely not being diagnosed.”
The lone star tick, Amblyomma americanum, can stay attached to a host for as long as seven days until it is fully engorged with blood. Bourbon virus is transmitted through that tick, and the CDC says it cannot rule out the virus being present in other parts of the country.
Cases across the US
Bourbon virus was first identified in 2014 in a man from Bourbon County, Kansas, and that patient died. In 2017, a 58-year-old woman in Missouri died after the virus went misdiagnosed for a significant period. This year, a lethal case in a 63-year-old diabetic male was reported in Kansas.
Those cases show the pattern researchers are worried about: the virus is rare, but it has already produced fatal infections in more than one state. The New York finding gives doctors in New York and the Northeast a reason to think beyond Lyme disease when a patient with tick exposure does not improve on doxycycline.
Researchers warned that Bourbon virus may become more prevalent this summer and in the years ahead, leaving diagnosis as the main bottleneck if more people fall ill. For readers in New York and the Northeast, the practical step is simple: a tick-related fever or severe illness that does not respond as expected should not be treated as a routine Lyme disease case without further review.
The remaining question is how many additional Bourbon virus cases may already be present but undiagnosed in New York and elsewhere.
