Rat-Borne Disease Reported In Berkeley, Health Officials Warn

BERKELEY, CA — Leptospirosis, a treatable but potentially deadly rat-borne disease, has been detected in and around a homeless encampment in Berkeley, public health officials announced Monday.

Numerous rats and at least two dogs tested positive in 2025 for leptospirosis at the homeless encampments on Harrison Street, just south of Albany and UC Berkeley's University Village, public health officials announced Monday.

Berkeley's Health Officer, Noemi Doohan, issued an alert on Monday, recommending that encampment residents move out of an area they're calling a red zone bound by San Pablo Avenue, Gilman Street, Codornices Creek and the Berkeley railroad tracks.

"Any items removed from encampments and exposed to mud and standing water should be disinfected," Doohan said in the alert. "Immediate departure from these encampments will reduce risk to encampment residents and their dogs, and to the surrounding neighborhood, while also allowing the City to mitigate the currently uncontained Leptospirosis contagion associated with the rat population."

Leptospirosis is a treatable disease commonly found in contaminated water or soil following a hurricane or flood. It spreads through the urine of infected animals, including dogs, livestock, and rodents and stays alive in impacted areas for 30 or more days, according to health officials.

Symptoms generally appear 2 to 30 days after a person comes in contact with the disease. People may experience flu-like symptoms, such as chills, a headache, and muscle aches, according to the Centers for Disease Control and Prevention.

More serious symptoms may appear during a second phase, including kidney or liver failure or meningitis. The disease can also appear asymptomatic. If not treated, the disease can lead to death.

In the United States, approximately 100 to 150 cases of leptospirosis occur annually. A few cases were reported in Chicago last fall.

Berkeley Health officials plan to treat the impacted zones by clearing out the encampments and then cleaning the area with soap and bleach.

UC Berkeley officials issued a statement Monday alerting members of the nearby university housing and warning residents to take standard precautions to avoid exposure. This includes practicing good hygiene, especially after coming in contact with any soil, protecting cuts and scrapes, avoiding Codornices Creek, wearing protective gear if working in landscaping or plumbing and keeping pets away from puddles or areas with potential rodent activity, university officials said.