An outbreak of a deadly rat-borne disease in Berkeley has claimed its first human victim in more than a decade — and health officials say the horrific case involved an RV so infested with rodents that nearly 200 rats had to be removed before the vehicle was destroyed.
Berkeley officials confirmed this week that one person died in May after contracting leptospirosis, a fatal bacterial disease spread through the urine of infected animals, especially mice. Another person who lived with the victim survived after being hospitalized for a long period.
The couple lived together in an RV about a mile from a sprawling homeless encampment in North Berkeley that has been at the center of an ongoing leptospirosis outbreak among rats and dogs since late 2025.
The two occupants were using the RV to catch, feed and raise wild mice, City Manager Paul Budenhagen said. Officials described the vehicle as “heavily infested” with rodents.
Vector control crews removed approximately 200 rats from the RV before it was towed and destroyed.
The two people “fell ill, but did not seek medical care for weeks and perhaps months,” Budenhagen wrote in a memo to the City Council. This delay is believed to have “contributed to the seriousness of their illness.”
The victim died shortly after being admitted to hospital, while the second resident eventually recovered.
Dr. Peter Chin Hong, an infectious disease expert at the University of California, San Francisco, said the sheer number of rodents greatly increases the risk of infection.
“The more mice you have, the more urine you have, and the greater the chance that at least one of the mice will become infected.” SFGATE said. “If you only have one mouse, it’s like playing mouse roulette.”
Leptospirosis usually begins with flu-like symptoms, including fever, chills, headache, muscle pain, nausea and vomiting, but can progress to life-threatening organ failure.
“It’s a two-part disease,” Chen Hong said. “The early stage is similar to flu symptoms.”
Despite the death, Chen Hong stressed that the disease is usually treatable when detected early.
“No one should die from lepto,” Chen Hong said. “It’s bacteria. It can be treated with antibiotics available in every hospital.”