Berkeley Resident Dies From Rare Rat-Borne Disease: Officials

BERKELEY, CA — One person is dead, and another has recovered after contracting a rare rat-borne disease in Berkeley, city officials said.

City officials said in a public health update Wednesday that the pair had contracted leptospirosis in May while living in a rat-infested RV about one mile from a homeless encampment along Harrison Street.

The city first detected the disease, which is spread through rat urine, in the encampment along Harrison Street back in late 2025. Numerous rats and at least two dogs tested positive for the disease at the time, but no human cases had been reported.

The city designated the area around the encampment as a "Red Zone" and recommended that residents move out as soon as possible to mitigate health risks.

In May, city officials confirmed the first human cases of leptospirosis, the first in Berkeley in more than a decade.

The cases were severe because of delayed access to medical care, officials said. Both were hospitalized, but one died, city officials said.

The risk of contracting leptospirosis remains low for the "vast majority" of Berkeley residents and business owners as of Wednesday, according to officials.

But given "new evidence" that high-leptospirosis-positive rat populations are not limited to the Harrison Street corridor, the city is shifting to a broader approach to mitigate the health risks in other parts of the city.

To combat the spread of the disease, Berkeley has already tested the water in Codornices Creek, removed 40 tons of garbage and debris from the Harrison Street corridor and done community outreach.

There are only a few hundred cases of leptospirosis in the United States each year. Person-to-person spread is rare, but risks are higher if living among rodents or animal urine.

The disease infects about 1 million people a year globally and kills about 60,000, according to the Centers for Disease Control and Prevention.

According to the California Department of Public Health, "leptospirosis is rare in California, and most infected Californians are exposed in another state or country."

The Golden State averages 2.8 human cases per year, generally in patients who traveled from Hawaii or tropical countries, according to the National Institute of Health.

Fatal cases are extraordinarily rare nationwide, averaging 10 or 11 per year between 2014 and 2020, the National Institute of Health. Most of those cases involve international travel.