Fleaborne Typhus Is Rising in Los Angeles County, and in 2022 It Killed Three

Fleaborne typhus is usually a moderately severe illness that rarely kills: among patients treated with the antibiotic doxycycline, fewer than 1% die. But in Los Angeles County (LAC), California, reported cases climbed from 31 in 2010 to 171 in 2022 — and between June and October 2022, three people died of it, a case-fatality rate of 1.8%.

The disease

Also called murine typhus, fleaborne typhus is caused by the bacterium Rickettsia typhi. People are infected when flea feces are rubbed into a flea bite, a scrape or the mucous membranes. The Oriental rat flea is the historical carrier, but in U.S. suburbs the main one is the cat flea, which lives mostly on domestic cats but also on opossums, dogs and rats.

• Symptoms: fever, headache, a rash that spares the palms and soles, hepatitis and low platelet counts.
• Severity: about a third of patients need intensive care for complications such as aseptic meningitis, seizures, respiratory distress syndrome or septic shock.
• Where: most U.S. cases are in California, Hawaii and Texas. In Texas, 11 of 3,048 cases (0.4%) during 1985–2015 were fatal. The disease is endemic in LAC, and reporting it is mandatory in California.

Three deaths

All three patients were Hispanic adults with underlying health problems.

Patient B's story shows how easily the disease is missed. After two days of headache and fever, an urgent care clinic tested her for COVID-19 (negative) and prescribed allergy medicine. Five days later she went to an emergency department with fever, chills, night sweats, headache and back pain, got fluids and was sent home. The next day she was admitted with sepsis. On her second hospital day her heart raced and twice stopped; she was resuscitated, and an infectious diseases physician, noting her headache, fever and abnormal liver tests, started doxycycline for possible typhus. She died of multiorgan failure the next day. The autopsy found myocarditis, with rickettsial antigens in the small blood vessels of her heart.

Patient C was brought to an emergency department after lying in one spot on the ground for 24 hours, feverish and disoriented, with a petechial rash on his legs and torso. Treated for suspected meningitis, typhus and neurosyphilis, he developed respiratory failure and multiorgan failure and died on his fifth hospital day.

Why cases may be rising

The spread of cat fleas, which infest both free-roaming and pet animals, may explain rising cases in suburbs; more rodents in LAC's cities and suburbs could also contribute. Texas, too, is seeing more cases over a wider area. With more cases, more severe ones and deaths are likely to be found; a change in the bacterium's virulence has not been documented but should be watched for. Fleaborne typhus is no longer nationally notifiable, which makes surveillance harder.

What doctors and the public can do

• Suspect it in anyone with fever, headache and rash, especially someone who lives in or has visited an area where the disease is endemic, or has been around rodents, opossums or feral cats. Myocarditis from R. typhi has been reported in such areas and should be considered in a patient with acute coronary syndrome and an unexplained fever.
• Treat immediately. Antibody tests can be negative early, and confirmation requires a fourfold rise between early and later samples; commercial PCR testing isn't available. Don't wait: start doxycycline as soon as typhus is suspected.
• Control fleas. There is no vaccine. Veterinarian-approved flea control on pets reduces exposure, and monitoring fleas on rodents, opossums, cats and dogs — and how many are infected — can guide prevention.

Surveillance likely misses milder cases, since mostly severely ill patients are tested, and patients weren't followed after discharge, so some deaths may have been missed.

Sources

Based on Jemma Alarcón, Armine Sanosyan, Zuelma A. Contreras, et al., "Fleaborne Typhus–Associated Deaths — Los Angeles County, California, 2022," Morbidity and Mortality Weekly Report, volume 72, Centers for Disease Control and Prevention; a work of the United States government in the public domain.