New York City officials have a mystery on their hands: There have been three recent cases of humans falling ill — including one fatality — with a rare disease that’s transmitted through rat urine, all in the same neighborhood of the Bronx.

The Department of Health and Mental Hygiene says in an alert issued on Tuesday [PDF] that this is the first time a cluster cases of leptospirosis has been identified. There were just 26 cases reported to the city between 2006 and 2016, with eight of those reports coming from the Bronx.

The three recent cases were identified over the last two months in a one-block section of a Bronx neighborhood. It’s already rare for humans to catch leptospirosis, but person-to-person transmission isn’t common either, the department says.

All three victims had severe illness and were hospitalized with acute kidney and liver failure, the alert says, while one person who developed a pulmonary hemorrhage died as a result of an infection it caused. The other two people have since been released from the hospital.

In NYC, most human cases are associated with exposure to rats, as infected animals may excrete bacteria into the environment. Rat urine can enter the body through your eyes, nose, or mouth, or through wounds and cuts in your skin, the department says. Infection can also occur if you come into contact with infected animals, soil, or food, but again, officials note, it is rarely transmitted from person to person.

The illness is serious but it can be treated with common antibiotics. As such, city agencies have taken “immediate measures” to reduce the rat population in the area and are spreading the word about symptoms and treatments to tenants.

Though some who are infected may show no symptoms, others may experience a fever, headache, chills, muscle ache, vomiting, or diarrhea.

Officials recommend washing hands thoroughly if you come into contact with areas where rats may live; always wearing shoes while taking garbage to the trash compactor room; and avoiding contact with rats or places where they may have urinated. Healthcare providers are urged to report any suspected cases immediately to the department, by calling the Provider Access Line at (1-866-692-3641).

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