for Prevention

Preventing Flea-borne Typhus in Los Angeles County

September 2019

Van Ngo, MPH

Zuelma Contreras, MPH

Mireille Ibrahim RN, MPH

Dawn Terashita, MD

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Flea-borne typhus, also known as murine or endemic typhus, is a disease transmitted by fleas infected with Rickettsia typhi or Rickettsia felis. Typhus is endemic to Los Angeles County. Cases can occur year-round but typically increase through the late summer and fall. As we are currently in peak typhus season, it is important for clinicians to be aware of the prevalence and risk of typhus. A summary of typhus disease trends in LA County, transmission, clinical presentation, diagnosis, treatment, and prevention is presented below.


Key Messages

  • Flea-borne typhus*, caused by Rickettsia typhi or Rickettsia felis, is endemic in LA County. Cases occur year-round and can be found in all areas of the county.
  • Clinicians should consider flea-borne typhus in patients with a non-specific febrile illness with headache, myalgia, rash, and laboratory abnormalities including leukopenia, thrombocytopenia, and elevation of hepatic transaminases, without alternate identifiable etiology.
  • Typhus is easily treated with doxycycline. Patient treatment should not be delayed pending diagnostic tests.
  • Report all clinical diagnoses and/or positive laboratory results for flea-borne typhus to the local health department by electronic transmission (including fax), telephone, or mail within 7 calendar days of identification.

*Flea-borne typhus should not be confused with typhoid fever, which is caused by Salmonella typhi and spread by contaminated food and water.


Disease Trends in LA County

LA County has experienced record-breaking increases of flea-borne typhus in recent years, culminating in 2018 with two outbreaks in the areas of Downtown LA and Willowbrook and a record high annual count of 109 cases (see graph below). The risk of typhus is present everywhere in the county, with cases occurring countywide each year (see map below). Typhus cases are seen to cluster in areas where environmental factors, either natural or man-made, support animal populations that carry infected fleas.

It is likely that many cases go unreported, as infections are often mild and may not be diagnosed. The majority of typhus cases that are reported to LAC DPH are hospitalized.


Flea-borne Typhus Cases by Year, LAC*

Typhus cases 2000-2018

*Excluding Long Beach and Pasadena
Source: LA County Department of Public Health, Acute Communicable Disease Program



Los Angeles County* Flea-borne Typhus Case Distribution by City

Map of Typhus Cases 2014-2018

*Includes data from Long Beach and Pasadena
Source: LA County Department of Public Health, Acute Communicable Disease Program



Typhus is transmitted to people through contact with the feces of a flea infected with R. typhi or R. felis. The primary animals known to harbor infected fleas include rats, feral cats, and opossums. People with exposure to animals and their infected fleas are at risk of acquiring flea-borne typhus. Pet dogs and cats that spend time outside may also come in contact with infected fleas and can carry them to humans. Infected animals are not known to get sick from flea-borne typhus. Typhus cannot be transmitted from person-to-person.


Clinical Characteristics

Typhus symptoms typically occur 7 to 14 days after exposure. Typhus presents as a non-specific febrile illness. Symptoms may include headache, chills, myalgia, abdominal pain, and/or vomiting. A rash, typically maculopapular, may appear after 1 week, but may also be absent altogether. Laboratory abnormalities include leukopenia, thrombocytopenia, and elevation of hepatic transaminases. Flea-borne typhus may be a mild, self-limited illness, or can present as severe disease requiring hospitalization. Fatalities occur in less than 1% of cases. Severe cases may result in renal, respiratory, ophthalmologic, cardiac, or neurologic dysfunction. Adults with advanced age or G6PD deficiency are at greatest risk for severe disease.



A presumptive diagnosis of typhus should be made based on clinical presentation and exposure history. While a history of exposure to fleas or outdoor animals supports the diagnosis, it is important to note that often cases have no known environmental exposures.

The diagnosis should be confirmed with serologic testing for Rickettsia typhi IgG and IgM antibodies. As there can be cross-reactivity with other Rickettsiae, LAC DPH also recommends testing for antibodies against R. rickettsii, the causative agent of Rocky Mountain Spotted Fever.

The indirect immunofluorescence antibody assay is the preferred serologic test as it can provide quantitative results. As serology performed on samples collected within the first week of symptom onset can often be falsely negative, confirmation of R. typhi diagnosis requires a four-fold increase in IgG titers in paired serologic samples. These samples should be collected during the acute stage (in the first two weeks of illness or while the patient is experiencing symptoms) and in the convalescent stage (2 weeks later). However, if the patient does not return for the convalescent sample, a probable typhus diagnosis can be made with a single positive IgG or IgM sample plus supportive clinical data.

Testing is available at many commercial laboratories and is free of charge at the LAC Public Health Laboratory (PHL). For more information on submitting specimens to LAC PHL, see the laboratory testing guidelines on the LAC DPH flea-borne typhus testing webpage.

For more detailed information on testing, consult the “How do you test for flea-borne typhus” section from the Centers for Disease Control and Prevention's flea-borne typhus Clinical FAQs.



Treatment decisions should be based on clinical presentation. Treatment should not be delayed pending laboratory confirmation.

Flea-borne typhus is readily treated with antibiotics. Doxycycline is the treatment of choice; the dose of doxycycline for adults is 100 mg orally BID. Treatment should occur for at least 48 hours after the patient becomes afebrile or for seven days, whichever is longer.



Typhus patient education flyer


Download this and other patient education resources.

Health care providers should counsel patients on how to reduce exposure to infected fleas including the following:

  • Store trash and other food sources in secured bins and/or clear it away from places of residence to avoid attracting animals.
  • Maintain the yard to remove debris and trim overgrown plants and bushes.
  • Discourage animals from nesting around the home by closing crawl spaces and attics and trimming or removing vegetation around buildings.
  • Avoid petting or feeding stray animals.
  • Use flea control products for domestic pets.
  • Consider using EPA–registered insect repellents labeled for use against fleas when outside.
  • Call the LAC DPH Veterinary Public Health Program at 213-989-706 with concerns regarding pets.
  • Call Environmental Health Vector Management Program at 626-430-5450 with concerns regarding wild animals or rodents.



Flea-borne typhus and other rickettsial infections are reportable in California and health care providers are mandated to report all suspect and confirmed cases based on clinical diagnoses and/or labs to the local health department within 7 calendar days. Reporting of cases helps LAC DPH to target surveillance and health education activities.

For cases in LA County, a standard Confidential Morbidity Report (CMR) can be used to file a report which can be either faxed or mailed. During normal business hours, from 8 AM to 5 PM, cases can also be reported by telephone to 888-397-3993.

For cases among residents of the cities of Long Beach or Pasadena, please contact their local health department.



The increasing number of typhus cases in recent years emphasizes the importance of preventing and controlling its spread. Health care providers can play a critical role in prevention by recognizing and reporting typhus cases and educating patients on prevention. Clinicians can stay up to date on weekly typhus case counts, FAQs, flea prevention guidance, and other patient resources by consulting the LAC DPH flea-borne typhus webpage.




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Author Information:

Van Ngo, MPH
Supervising Epidemiologist

Zuelma Contreras, MPH, PhD

Mireille Ibrahim RN, MPH
Epidemiology Analyst

Dawn Terashita, MD
Associate Director

Acute Communicable Disease Control

County of Los Angeles
Department of Public Health

Rx for Prevention, 2019

Published: September 23, 2019