A new report says a Rochester, NY., hunter may have developed an ultra-rare brain infection after eating the brains of squirrels he killed, according LiveScience.

The report was presented at the ID (infectious disease) week conference as an abstract called “Towards Earlier Diagnosis of Transmissible Spongiform Encephalopathies (TSEs): A Case Series, Including One Associated with Squirrel Brain Consumption.”

The report identified a 61-year-old male who was diagnosed with the rare brain infection called variant Creutzfeldt-Jakob Disease after eating squirrel brains. He arrived at a hospital after suffering thinking problems and an impaired walk, according to the report. He died about five months after being diagnosed with the infection in 2015.

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The disease is similar to “mad cow disease,” which causes tiny holes to fill the brain until the tissue looks like a sponge (which is where ‘”spongiform” comes from), according to the National Institutes of Health.

The infection is always fatal, and most who get the disease live around a year. It causes rapid degeneration of memory, thinking, vision and coordination before causing dementia and death, according to the NIH.

It is part of a family of diseases caused by prions, which are infectious proteins that infiltrate the brain. Chronic wasting disease in deer is one example of a prion disease, as is fatal familial insomnia, a different brain infection affecting humans that removes the ability to sleep, eventually causing death.

Variant Creutzfeldt-Jakob disease is extremely rare, with only four people ever confirmed to have the disease in the U.S., according to the Centers for Disease Control.

The non-variant Creutzfeldt-Jakob Disease is also rare, with only about 350 cases per year in the United States, according to the NIH. Most people develop the disease spontaneously, while a few inherit it. Some acquire it through other means, such as by ingesting infected tissue - which is what scientists suspect happened with the squirrel brains.

Tara Chen, a medical student who produced the report, said it wasn’t entirely clear yet if the squirrel brains were the cause of the infection, and that researchers were trying to secure autopsy samples, according to LiveScience. Chen said it also wasn’t clear if the man ate the brains themselves or meat that was contaminated with brain matter, according to the site.

Squirrel-brain transmission of the disease is not a new concern. Doctors in Kentucky put out a warning against eating squirrel brains in 1997 after 11 people were diagnosed in the state with the non-variant Creutzfeldt-Jakob Disease, according to the New York Times.

“‘All of them were squirrel-brain eaters,’‘ a doctor told the paper at the time.