The Los Angeles County Department of Public Health (LAC DPH) is reporting an endemic flea-borne typhus outbreak in downtown Los Angeles. Between July and September 2018, health officials identified nine cases of flea-borne typhus.

Soon the proventriculus, or esophagogastric junction will become blocked with a bacterial mass preventing the flea from swallowing food.

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.

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.

Flea-borne typhus, also known as murine or endemic typhus, is a disease transmitted by fleas infected with Rickettsia typhi or Rickettsia felis.

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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.

Person-to-person transmission does not occur. Humans are a dead-end host for flea-borne typhus.

Flea-borne typhus is readily treated with antibiotics. Doxycycline is the treatment of choice.