California and Texas have both experienced a rise in typhus cases in recent years, according to health officials.
Los Angeles County has logged a record 220 cases of flea-borne typhus in 2025, with nearly 90% of those infected requiring hospitalization, officials said on Thursday.
The tally exceeds the 187 cases counted in 2024 and continues a general rise that began in 2021, when 141 infections were recorded. Health authorities confirmed localized outbreaks in Santa Monica, the Willowbrook neighborhood of South Los Angeles, and Central Los Angeles.
The bacterial illness, caused by Rickettsia typhi and spread by fleas that feed on rats, opossums, and stray cats, is not transmitted between people. Infection usually occurs when flea feces, known as flea dirt, are rubbed into a bite wound, scrape, or the eyes.
Symptoms typically emerge one to two weeks after exposure and include high fever and chills, severe headache, body aches and muscle pain, nausea or vomiting, and a distinctive rash. The disease is treatable with antibiotics if caught early.
“Flea-borne typhus can cause serious illness, but it is preventable with simple steps,” Los Angeles County Health Officer Dr. Muntu Davis said, The Santa Monica Mirror reported. “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.”
The disease has also resurged sharply in Texas. Dr. Gregory Anstead, a professor in the Division of Infectious Diseases at UT Health Science Center at San Antonio and a staff physician at the Audie Murphy VA hospital, has tracked the increase and linked it to population growth and warming temperatures.
“I’ve reexamined the data and found that the number of cases went from 307 in the decade of the 1990s up to 3,750 in the decade of 2010 to 2019. So that’s basically a 12-fold rise in the state of Texas,” Anstead said, the Texas Standard reported.
The illness had declined after a massive public health program of rat extermination and flea spraying, but began rising again around 2000. It has spread from its traditional base in South Texas to counties including Bexar, Travis, Harris, Dallas, and Tarrant.
Anstead attributed part of the influx to explosive population growth, which has increased the number of pet dogs and cats serving as flea hosts. Warmer temperatures tied to climate change and the urban heat island effect have also contributed.
“Fleas are more likely to have more vigorous biting of pets when they’re hotter; they have more mating when they’re warmer,” Anstead said. “And then the other thing is that the warmer temperature also accelerates the growth of the bacteria inside the flea.”
While the nationwide mortality rate is less than 2%, the disease can produce severe complications.
“It can cause very serious manifestations in the brain and the heart, in the liver, in the kidneys, in the lungs. It can cause septic shock. And about one-third of those that are affected end up in the ICU for some period of time,” Anstead said. “We had a case in San Antonio where a 16-year-old girl got this disease. She went into septic shock. She ended up losing parts of three limbs from the septic shock.”
There is no vaccine, so Anstead said the focus must remain on prevention.
“People who have had cats and dogs should not take this lightly that they need to provide year-long protection for their pets, which also protects them,” Anstead said.
He also recommended trap-neuter-release programs for stray animals and insecticide spraying in areas with heavy flea contamination.
Public health officials in California noted that infected animals often appear healthy yet carry fleas indoors on pets or into yards. Cases have affected residents ages 1 to 85, though people living outdoors or in rodent-infested housing face elevated risk. While deaths remain uncommon, three adults with underlying conditions died from the disease in 2022 in Los Angeles County.
To limit spread, health officials urge year-round flea-control treatments on all pets and recommend keeping them indoors when possible. Residents should also use secure, tightly lidded trash cans, clear yard debris, seal crawl spaces and other entry points, and avoid feeding or handling stray animals. EPA-registered insect repellents can provide additional protection.
Officials advise anyone with symptoms, especially after possible exposure to fleas, to contact a health care provider promptly.