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LAC DPH Health Alert: Outbreak of Flea-Borne Typhus in Downtown Los Angeles

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This message is intended for internal medicine, infectious disease, family medicine, pediatrics, emergency medicine, and urgent care providers. Please distribute as appropriate.

Key Messages

• An outbreak of endemic flea-borne typhus has been identified in downtown Los Angeles. Six of the nine cases have occurred in persons experiencing homelessness.

• Clinicians should consider flea-borne typhus in patients with febrile illness of unknown etiology (see clinical presentation below).

• Report suspect cases of flea-borne typhus to Los Angeles County Department of Public Health within 1 working day.

• Typhus is not person-to-person transmissible, use standard contact precautions for patients.


Between July and September 2018, the Los Angeles County Department of Public Health (LAC DPH) identified nine cases of flea-borne typhus associated with downtown Los Angeles. The cases have a history of living or working in downtown Los Angeles and six of them have reported experiencing homelessness or living in interim housing facilities in the area. All cases were hospitalized, and no deaths have occurred. LACDPH is working with the City of Los Angeles to identify and reduce the environmental risk for exposure to typhus.


Flea-borne typhus, also known as murine or endemic typhus, is a disease transmitted by fleas infected with Rickettsia typhi or Rickettsia felis. Flea-borne typhus is endemic in LAC with cases detected each year. In recent years, the average number of cases
reported to LAC DPH has doubled to nearly 60 cases per year; however, geographic clusters of the size occurring in downtown Los Angeles are unusual. Most cases occur in the summer and fall months.
In LAC, the primary animals known to carry infected fleas include rats, feral cats, and opossums. People with significant exposure to these animals are at risk of acquiring flea-borne typhus. Pet dogs and cats that are allowed outside may also come in contact with infected fleas and could carry them to humans. Infected animals are not known to get sick from flea-borne typhus.

Diagnosis requires a high degree of clinical suspicion as flea-borne typhus typically presents as a non-specific febrile illness and early diagnostic tests are unreliable. Severe complications can occur resulting in lengthy hospitalizations and rarely death.

Actions Requested of Providers
• Consider a diagnosis of 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.

• Report all suspected cases of flea-borne typhus, particularly in persons experiencing homelessness or with significant exposure to downtown Los Angeles, to LAC DPH within 1 working day.

Clinical Presentation

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


As symptoms are non-specific and laboratory testing is unreliable in acute phases of infection, treatment decisions should be based on clinical presentation and exposure history. Treatment for patients with suspected flea-borne typhus should not be delayed pending diagnostic tests.

Laboratory diagnosis can be conducted through serologic testing for R.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. Serology performed on samples collected within the first week of symptom onset can often be false-negative. Confirmation of R. typhi diagnosis requires paired serology of acute and convalescent samples (drawn 2 weeks later) demonstrating a four-fold increase in IgG titers. However, as not all patients return for additional testing, a probable diagnosis can be made with a single positive sample plus supportive clinical and laboratory data.

Serological tests for R. typhi and R. rickettsii are available at most commercial laboratories. Testing is also available at LAC DPH Public Health Laboratory as part of a Rickettsial Antibody Panel. For more information on submitting specimens to PHL, see the laboratory testing guidelines on the LAC DPH Flea-Borne Typhus Testing webpage.


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 a minimum of five days or until 48 hours after patient becomes afebrile. Treat suspect cases promptly; do not wait for laboratory confirmation.


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.
• Discourage animals from nesting around your home by closing up crawl spaces and attics and trimming or removing vegetation around buildings.
• Avoid petting or feeding stray animals.
• Use flea control products for domestic pets.
• When outside, consider using EPA–registered insect repellents.

Visit the LAC DPH Flea-Borne Typhus webpage for FAQ, flea prevention guidance, and other patient resources.

Transmission and Infection Control
Person-to-person transmission does not occur. Humans are a dead end host for fleaborne typhus. Standard precautions are indicated. Patients should contact their local animal control agency to report feral cats and opossums.

Los Angeles County DPH Acute Communicable Disease Control Program
• Weekdays 8:30 AM – 5:00 PM: call 888-397-3993. For consultation: call 213-240-7941.
• After hours: call 213-974-1234 and ask for the physician on call.

Long Beach Health and Human Services
• Weekdays 8:00 AM – 5:00 PM: call 562-570-4302
• After hours: call 562-500-5537 and ask for the Duty Officer.

Pasadena Public Health Department
• Weekdays 8:00 AM – 5:00 PM (closed every other Friday): call the
Communicable Disease Control Program at 626-744-6089
• After hours: call 626-744-6043.

Additional Resources

• Los Angeles County Department of Public Health Flea-borne Typhus webpage www.publichealth.lacounty.gov/acd/VectorTyphus.htm
• California Department of Public Health Flea-borne Typhus webpage www.cdph.ca.gov/Programs/CID/DCDC/Pages/Typhus.aspx
• Centers for Disease Control and Prevention Murine Typhus webpage www.cdc.gov/typhus/murine/

This Health Alert was sent by Dr. Sharon Balter, Director, Division of Communicable Disease Control and Prevention, Los Angeles County Department of Public Health.

To view this and other communications or to sign-up to receive LAHANs, please visit http://publichealth.lacounty.gov/lahan

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