Flea-Borne Typhus Is Rising in LA—What You Need to Know

Amid a continued rise in flea-borne typhus cases across L.A. County, infectious disease experts at Cedars-Sinai are urging residents to take precautions to reduce their risk of infection.

“If you have pets that spend time outdoors, it’s important to take steps to prevent fleas, such as using flea control products,” said Jonathan Grein, MD, director of Hospital Epidemiology and associate professor in the Department of Medicine at Cedars-Sinai. “Typhus is not usually life-threatening, but if it’s untreated, it can result in severe illness.”

Flea-borne typhus, also known as murine typhus, is caused by the bacterium Rickettsia typhi and is transmitted to humans by infected fleas.

According to the L.A. County Department of Public Health, a record 220 cases were reported in 2025—continuing a steady upward trend observed since 2010. At Cedars-Sinai, several patients required hospitalization for flea-borne typhus last year.

“While cases tend to peak in late summer and early fall, expanding urban wildlife habitats and warmer weather are likely contributing to increased transmission year-round, so we want people to be aware,” Grein said.  

The Cedars-Sinai Newsroom spoke with Grein about how flea-borne typhus spreads, its symptoms, treatment and ways to prevent infection.

How do people get flea-borne typhus?

Flea-borne typhus primarily circulates among rats, opossums and stray cats. Fleas that feed on these animals can become infected and then transmit the bacteria to humans through flea bites and flea feces—which enter the body through small breaks in the skin or when rubbed into the eyes.

Pets that spend time outdoors may carry infected fleas into the home, increasing the risk of human exposure. Because many fleas can feed on a single infected animal, the disease can spread and grow quickly within animal and flea populations, making outbreaks likelier to occur among humans.

Is flea-borne typhus contagious?

No. The disease is not spread from person to person; transmission occurs only through infected fleas.

What are the symptoms?

Symptoms are often flu-like and may include fever, headache and muscle aches. Sometimes people will develop a rash on the trunk or back of the body about one to two weeks after symptoms begin. While many cases resolve on their own within about a week, treatment is recommended because some people can develop complications affecting the brain and other organs.

How serious is typhus?

Flea-borne typhus is generally not life-threatening and is typically easy to treat. However, people who are pregnant or have a compromised immune system face a higher risk of severe illness.

Is typhus the same as typhoid?

Typhus is sometimes confused with typhoid fever. While the two have similar names and overlapping symptoms, they are caused by very different pathogens and are not related.

When should someone see a doctor?

Anyone who may have been exposed to fleas and develops persistent fever, severe headache and muscle aches within one to two weeks should seek medical care. A simple blood test is used to diagnose typhus, and early treatment helps prevent complications.

How is it treated?

Treatment typically involves the antibiotic doxycycline for about a week. Most patients respond quickly, with symptoms resolving soon after treatment begins.

How can people prevent flea-borne typhus?

Prevention centers on minimizing exposure to fleas. Keep pets on year-round flea control, avoid contact with wild or stray animals, and keep them away from areas where pets live or eat. Securing trash bins and controlling rodent populations around the home also can help reduce the spread of fleas between animals, and ultimately, to humans.

Read more from Cedars-Sinai Stories and Insights: Stay Healthy as Beach Weather Beckons