New York City is investigating three recent cases — one of them fatal — of a rare disease transmitted through rat urine that have occurred in the Grand Concourse neighborhood of the Bronx, according to the Department of Health and Mental Hygiene.

This is the first time a cluster of the cases of the disease, leptospirosis, has been identified, according to an alert issued by the department on Tuesday. From 2006 to 2016, 26 cases were reported in the city; the Bronx had the highest number, eight.

The three most recent cases occurred in the past two months. All the patients became severely sick and were hospitalized with acute kidney and liver failure, the health department said. One died as a result of an infection. The two who survived have been released from the hospital.

The sexes and ages of those infected were not available. The department did not specifically identify the location of the cluster.