Fleaborne typhus cases climbing in LA County, CDC says

By Giri Viswanathan and Deidre McPhillips, CNN

(CNN) — Fleaborne typhus is on the rise in Los Angeles County, with reported cases nearly tripling over the past decade, from 31 in 2010 to 171 in 2022. The disease can be severe but is rarely fatal, and three deaths last year — the first in nearly 30 years in the county — led the US Centers and Disease Control Prevention to investigate.

General signs and symptoms of fleaborne typhus include fever, headache, rash, liver inflammation and low blood platelets. The disease spreads to humans from infected fleas that often live on rodents, opossums, or cats, both pets and feral. It can’t be spread from person to person, the CDC says.

Fleaborne typhus cases have been rising in LA County for the past decade, and the region hit its highest number in 2022. Experts believe that this increase could be due to two factors: increased physician awareness — and diagnosis — of fleaborne typhus, and increased interactions between humans and opossum and cat populations that carry the typhus flea.

For Dr. Umme-Aiman Halai, a medical epidemiologist at the Los Angeles County Department of Public Health and one of the study’s authors, that “big surge” is concerning. She hopes her team’s report raises awareness among health care providers to recognize and treat the disease early.

“We want to educate the public on the steps that they can take to reduce their risk,” she said. “These three deaths are a wake-up call to start thinking about this disease and the severe manifestations and the effect on our communities.”

While there is no vaccine to prevent fleaborne typhus, a specific antibiotic — doxycycline —can treat it. Less than 1% of patients who receive doxycycline die from the bacterial infection.

The three adults who died from fleaborne typhus in LA last year all came into the health care system with some combination of symptoms associated with fleaborne typhus, according to the CDC report. Severe disease looked different for each, with a wide range of conditions including myocarditis, or inflammation around the heart; hemophagocytic lymphohistiocytosis, or a build-up of white blood cells that can damage organs; and septic shock.

Diagnostic testing for fleaborne typhus can miss early cases because antibody levels often aren’t high enough to detect until the disease has progressed.

To avoid delay in treatment, “health care providers should consider fleaborne typhus in any patient with fever, headache, and rash, particularly if the patient lives in or recently traveled to an area with endemic disease or had exposure to a reservoir animal (e.g., rodents, opossums, or feral cats),” according to the CDC report.

According to Dr. Jemma Alarcón, an epidemic service intelligence officer at the CDC and a study author, that means health care providers should begin treating for typhus if it seems likely that the patient has the disease, even before test results come back.

“They can treat for fleaborne typhus before they even get the diagnosis if it’s on their differential,” she said. “Because prompt treatment helps save lives.”

Cases of fleaborne typhus are required to be reported in California, but not nationwide. While this poses challenges to understanding the full scale of the disease spread, the CDC report notes that Texas, like LA, is also experiencing a “substantial increase in the prevalence and geographic distribution of fleaborne typhus.”

Cases are also identified in Hawaii each year, according to the state health department, though the true burden of disease in Hawaii and elsewhere is likely undercounted as patients with milder disease may not seek treatment or testing.

Using flea control products, like flea collars, is a key step in preventing pets from harboring typhus-infected fleas, experts agree. Alarcón suggested that they should also prevent their pets from interacting with “free-roaming” strays and wild animals like rodents and opossums, as well.

And to protect themselves, she warned, people should limit their interactions with wild, potentially infected animals.

“This is particularly important in endemic areas,” Alarcón told CNN. “Whenever they feed stray animals, they may also inadvertently be exposing themselves to these fleas, too. So just making sure that the environment is clean, that there’s not litter around, and that they don’t have much interaction with a stray animal.”

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