Avian Flu Diary: Los Angeles: County Public Health Reporting An Increase In Flea-Borne Typhus Cases

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Murine Typhus, aka flea-borne typhus, is a bacterial disease caused Rickettsia typhi - and while no longer terribly common in most of the United States - it is most often reported in California, Texas and Hawaii (see 2017's Texas: DSHS Issues Murine Typhus Alert).

Not to be confused with Typhoid Fever - which is caused by a Salmonella Typhi infection that can (rarely) be transmitted from one person to another - Typhus is acquired from contact with infected fleas that live on rodents, possums, raccoons and cats.

Although some cases recover without treatment, others can become sick enough to require hospitalization, and deaths are not unheard of (see 2023 MMWR Fleaborne Typhus–Associated Deaths — Los Angeles County, California, 2022)

The Rise of Typhus in LA County Since 2010

Through the use of vector control methods (including liberal use of DDT during the 1950s and 1960s), the number of cases dropped from > 5400 in 1944 to less than 100 in 1956 (cite). By 1987, incidence had dropped low enough that Murine Typhus was no longer a reportable disease (see chart below).

But over time, DDT lost much of its effectiveness - and was eventually banned in 1972 for environmental reasons - which coincidentally was the year with the lowest case count (n=18). While cases remained low well into the early 2000s, the lack of reporting requirements likely affected the numbers.

In recent years - particularly in Texas and more recently in California - we've seen a resurgence of murine typhus, which led the CDC to release a 1-hour webinar in March of this year which is archived on the COCA Call Website.

Yesterday the Los Angeles County Department of Public Health issued the following news release on a growing number of Typhus cases in Central Los Angeles (and now, apparently Santa Monica).

August 28, 2025
Public Health Reporting an Increase in Flea-Borne Typhus Cases in Los Angeles County

People urged to take precautions to protect themselves and their pets
The Los Angeles County Department of Public Health is urging people to take precautions following an increase of flea-borne typhus cases across the County. Earlier this year, Public Health investigated a localized outbreak of flea-borne typhus in Central Los Angeles and is currently investigating a second outbreak in the City of Santa Monica.
Flea-borne typhus cases have been rising in Los Angeles County since 2010. In 2024, a record 187 cases were identified. So far in 2025, 106 cases have already been reported, higher than this time last year. Public Health expects additional cases and clusters to appear in the coming months, as flea-borne typhus infections peak in late summer and fall.
“This ongoing increase in flea-borne typhus highlights the importance of taking preventive steps to reduce the risk of infection,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer.
What is Flea-Borne Typhus (Typhus)?
Typhus is an acute febrile illness caused by Rickettsia Typhi bacteria, which is spread by infected fleas. People can become infected when flea feces are rubbed into cuts or scrapes on the skin or rubbed into the eyes.
In Los Angeles County, infected fleas are most commonly found on rats, free-roaming cats, and opossums. Pets such as dogs and cats that go outdoors can bring fleas into and around your home. Infected animals typically do not show signs of illness. Flea-borne typhus is not spread from person to person.
“Flea-borne typhus is serious, but preventable,” said Dr. Davis. “We urge people to take precautions by using flea control on their pets, avoiding contact with stray animals, and preventing wildlife from living in or next to their home or property. If you develop symptoms, such as fever, chills, or a rash, seek medical attention right away.”
How to Prevent Flea-Borne Typhus:
Public Health encourages people to follow these preventive steps to the risk of flea-borne typhus infections:
· Keep fleas off you and your pets.
When outside, use EPA-registered insect repellent labeled for protection against fleas.
Routinely use flea control products on your pets.
Keep pets indoors as much as possible.
· Avoid attracting wild or stray animals.
Don’t leave pet food or water outside.
Don’t feed or touch stray or wild animals.
Keep your yard free of debris and overgrown plants.
Store trash in containers with tightly fitting lids.
Close off crawl spaces and seal any openings where animals could enter, hide, or find food and water.
Report stray animals or signs of rodents or opossums near your property to local animal control officials.