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Health officials are warning residents to take precautions, including keeping pets up to date on flea medication, after a record number of flea-borne typhus cases were reported in Los Angeles County over the past year.
The Los Angeles County Department of Public Health said 220 flea-borne typhus cases were reported in the county in 2025, the highest on record. The department investigated three outbreaks in 2025, including one in Santa Monica.
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The county health department’s report indicates that California also had the highest number of flea-borne typhus cases in the modern era at 277. (The California Department of Public Health, whose Jan. 21 report noted that LA County had 165 flea-borne typhus cases in 2025, has not confirmed this number.) That’s more than double the number from 2016 when counting suspect, probable and confirmed cases. Mandatory electronic reporting for the disease started in 2011, and the vast majority of cases in California are usually reported in Los Angeles and Orange counties.
Typhus is a disease caused by the Rickettsia typhi bacteria and results in fever, chills, headache and a cough, along with a distinctive spotted rash called a petechial rash.
The bacteria is spread when infected fleas bite a person. As these fleas bite, they defecate, and when a person scratches the bite, flea feces can enter the bloodstream. LA county health officials said the fleas can spread from stray animals, as well as from rodents and opossums in the area.
“Flea-borne typhus can cause serious illness, but it is preventable with simple steps,” Dr. Muntu Davis, who is the Los Angeles County health officer, said in a statement. “With cases at an all-time high and most requiring hospitalization, it’s critical that people take simple steps now, such as routinely using flea control on their pets, avoiding contact with stray animals, and preventing wildlife from living in or around their homes.”
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A scanning electron micrograph of the Rickettsia typhi bacteria.
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Shannon Bennett, the chief of science and a microbiology curator at the California Academy of Sciences, said the disease has been around for centuries and is “as old as the plague.”
“It’s always a little disconcerting to be hit with an old, emerging infectious disease,” she told SFGATE, saying she’s concerned that people’s hygiene and living conditions could leave them at risk.
Bennett said a changing climate with warmer temperatures may help flea populations increase, which can lead to the spread of typhus.
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“It’ll help drive the flea population up, and it’ll increase their own developmental life cycles,” she said of warmer weather. She also said that as people encroach on wildlife areas, there’s more of a chance for these diseases to spread from animals to people.
Typhus can be treated with antibiotics, and deaths are rare, accounting for less than 1% of cases. But the disease is serious, and LA health officials noted that 90% of those with the disease end up needing to be hospitalized.
Dr. Monica Gandhi, an infectious disease expert at UC San Francisco, explained why the bacterial disease, which peaked in the U.S. in the 1940s, can be deadly.
“It’s not only a really high fever,” she said. “Also, the laboratory abnormalities can be dangerous. You have low clotting factors, low white counts and anemia.”
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Gandhi said a patient with low clotting factors is at risk of dangerous internal bleeding, including bleeding from the brain.
“This can make anyone really sick,” Gandhi said, saying young healthy people are as at risk as older populations.“The majority of people who used to get infected with Rickettsial were, like, people who hiked in wildlife and were out in nature. Now, we’re getting it from our pets.”