Why Is This Medieval Disease Striking LA County?

A medieval disease known as typhus is surging in Los Angeles County as the region grapples with growing homelessness, unsanitary conditions, and a major rat problem.

Flea-borne typhus, a bacterial disease transmitted to humans through infected fleas, reached an all-time high in the county in 2025, with 220 cases reported. That’s up from 187 cases the year before.

Nearly nine out of 10 people diagnosed with the disease in 2025 required hospitalization, according to the Los Angeles County Department of Public Health.

Dr. Dean Winslow is a Stanford professor and infectious disease physician with 50 years in medicine. He directed COVID-19 testing for the federal government and was nominated by President Donald Trump in 2017 to serve as assistant secretary of defense for Health Affairs.

When asked whether a typhus outbreak in one of America’s wealthiest cities indicates a broader health or sanitation failure, Winslow didn’t hesitate.

“Absolutely,” Winslow told the Daily Signal.

“It’s largely an issue of … people living in just horrible conditions in close proximity to rats,” Winslow said, describing rats as the primary hosts involved in the infection.

Those conditions are particularly relevant as LA continues struggling with homelessness.

Data from the Los Angeles Homeless Services Authority (LAHSA) indicates homelessness has increased 3.3% in LA County and 7.9% in the city.

Winslow identified homeless encampments as environments where people can be particularly vulnerable to exposure. because of their proximity to rats.

However, the problem extends beyond encampments.

Los Angeles was named the “rattiest city” in America in Orkin’s latest annual ranking, overtaking Chicago for the first time in more than a decade—a distinction the company said was “likely influenced by weather patterns, urban infrastructure, and human behavior.”

When asked what he would recommend to Los Angeles officials, Winslow said the No.1 action item would be to “get a handle again on rat control issues.”

In recent years, California has restricted some poisons traditionally used to kill rats.

In 2020, Gov. Gavin Newsom signed Assembly Bill 1788, which restricted most uses of four rodenticides because of their potential harm to mountain lions and other wildlife.

Winslow said the restrictions may be one possible factor hindering rat control, noting that pest-control efforts have increasingly relied on “rat traps” and “less potent” methods.

“Those may be two reasons why … the rat population is out of control [in LA]”, Winslow said.

Guidance from the Los Angeles County Department of Public Health urges residents to protect themselves by keeping pets on flea-control products, avoiding stray animals, keeping yards free of debris, securing trash in containers with tightly fitting lids, and reporting nearby rodents or opossums to local animal control.

LA Mayor Karen Bass’ office did not return the Daily Signal’s request for comment.