A Berkeley resident died in May after contracting leptospirosis while living in a recreational vehicle that harbored nearly 200 rats — the city's first confirmed human fatality from the bacterial disease in over a decade, officials announced Wednesday.

The death, and a second nonfatal infection in the same household, mark an inflection point in Berkeley's months-long leptospirosis response. City officials have quietly abandoned the geographic risk zones they built around a northwest Berkeley homeless encampment in January, acknowledging that the fatal case occurred a mile from those boundaries — in a completely different context. What Berkeley is now admitting, in policy if not in so many words, is that you can't draw a map around rats.

Berkeley Public Health confirmed Wednesday that two people who lived together in an RV contracted leptospirosis, a bacterial infection spread through contact with rat urine. One died shortly after being hospitalized in May; the other survived a lengthy stay in the hospital. Officials said both delayed seeking care for weeks, possibly months, after symptoms began — a delay that health experts say is often what turns a treatable infection into a fatal one.

Vector control crews removed close to 200 rats from the vehicle before it was towed and destroyed. Officials called the situation "extreme." The RV had been parked approximately one mile from the Harrison Street corridor in northwest Berkeley, the encampment where the city first detected leptospirosis in rats earlier this year and around which it established formal risk zones for residents and pets.

Those zones are now gone.

The city has shifted to what officials describe as a broader strategy focused not on geography but on the conditions that make transmission likely — particularly, environments with severe rat infestations and limited access to medical care. It is a significant, if quietly made, admission: the disease did not stay where the city told it to.

Dr. Peter Chin-Hong, an infectious disease specialist at UC San Francisco, told SFGate that the volume of rodents in the RV dramatically increased the statistical likelihood of exposure. "The more rats you have, the more urine you might have, and you increase the chance of at least one of the rats having infection," he said. "If you just had one rat, it's like playing rat roulette."

Chin-Hong was direct about the tragedy at the center of the case: leptospirosis is not supposed to be fatal. "Nobody should die of lepto," he told SFGate. "It is a bacteria. It is treatable by antibiotics that every hospital has." The disease becomes lethal, he explained, when it goes unrecognized — something that happens regularly because Bay Area clinicians rarely encounter it. "People misdiagnose it because it's not something that's very common in the Bay Area. You kind of have to diagnose it or suspect it to treat it the right way."

In response to the death, Berkeley Public Health has issued new guidance to local medical providers, urging them to consider leptospirosis when patients report rat exposure and present with compatible symptoms. The disease incubates for two to 30 days after exposure, usually manifesting within one to two weeks as fever, chills, headaches, and muscle aches — symptoms that can easily be dismissed as flu. About 10 percent of infections progress to serious disease affecting the kidneys, liver, and lungs.

Berkeleyside, which first reported the fatality on June 10, also reported that officials described the occupants as having been breeding rats — a detail that distinguishes this case from most rat-infestation scenarios and complicates the city's messaging around who is at risk.

Chin-Hong said the general public has little reason to panic. "People shouldn't be panicked," he told SFGate. "But I think it's a wake-up call that it's in our backyard." For people living in vehicles, encampments, or other settings where extreme rat infestations are possible, though, the wake-up call sounds louder — and the conditions that allowed it to happen have not changed.