Typhus from fleas is on the rise in LA County, CDC warns

close up photo of the front half of a cat flea's body and head

The cat flea (Ctenocephalides felis) can spread the bacterial disease typhus to humans. (Image credit: NNehring via Getty Images)

Typhus spread by infected fleas is on the rise in L.A. County.

According to a new Morbidity and Mortality Weekly Report, published Friday (Aug. 4) by the Centers for Disease Control and Prevention (CDC), L.A. County's annual rate of fleaborne typhus has increased fairly steadily since 2010. That year, officials reported 31 cases, whereas in 2022, 171 cases occurred. Last year's case count was the highest recently reported, with 2021 taking second place at around 140 cases. 

And in 2022, three people died of typhus from fleas, marking the area's first reported deaths from the disease in nearly three decades, the CDC reported.

Fleaborne typhus, caused by the bacterium Rickettsia typhi, can sometimes cause severe illness that can lead to organ injury and requires intensive care. But few people now die of the disease, with fatality rates estimated to be less than 1% in people who receive antibiotic treatment. Most cases completely resolve with antibiotics, but people can end up needing hospitalization if their disease goes unrecognized and untreated for some time. 

Related: California woman got typhus from a neighborhood rat 

The initial symptoms of typhus, including fever, body aches, vomiting and rash, typically appear five days to two weeks after a person's exposure to an infected flea. 

The recent deaths in L.A. County occurred in June, August and October of 2022 and affected three adults. The first, a 68-year-old man, was likely exposed to infected fleas and flea-carrying rats around the litter-strewn highway near his home. The second, a 49-year-old woman, may have been exposed through interactions with stray kittens in her backyard. And the last, a 71-year-old, was experiencing homelessness and was likely exposed at the encampment where he lived.

The three people had existing medical conditions that may have put them at higher risk for severe typhus. The first two had type 2 diabetes and high blood pressure, among other chronic ailments, and the latter had a history of alcohol use disorder and methamphetamine use.

Leading up to his death, the 68-year-old patient developed hemophagocytic lymphohistiocytosis (HLH), a condition where abnormal immune cells accumulate in the skin, spleen and liver, where they destroy blood cells and cause organ damage. The woman developed myocarditis, or inflammation of the heart muscle, and all three patients developed sepsis, a body-wide, life-threatening immune reaction.

"Although reports of HLH among patients with R. typhi infection are rare, these three fleaborne typhus-associated deaths highlight the range of potentially severe manifestations of this infection," the CDC report states.

Fleaborne typhus may be rising in L.A. County as the cat flea (Ctenocephalides felis), one of the main typhus-spreading flea species, becomes more common in the area. Cat fleas prey on both wild animals and pets. According to the report, "another possible reason could be an increase in rodent reservoirs in urban and suburban areas."

Texas has also seen a similar increase in fleaborne typhus, the report adds. This year, a Texas man's case made headlines when he had to have his hands, toes, and parts of his feet amputated due to complications from typhus he caught from a flea bite.

Nicoletta Lanese
Channel Editor, Health

Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.