Murine Typhus Is Staging a Comeback

"[Murine typhus] is clearly returning, and our understanding of the current burden is almost certainly underestimated."

Joanna Salzer, DVM, PhD, veterinary medical officer, leader, epidemiology team, CDC National Center for Emerging and Zoonotic Disease

"This disease came roaring back in the last 20 years to levels that we haven't seen since the late 1940s."

Christopher Paddock, MD, leader, microbiology and diagnostic team, CDC Clinician Outreach and Communication Activity

If you've never heard of murine typhus, you're not alone. Also known as flea-borne, rat, urban, or endemic typhus, this disease had largely disappeared from public awareness in the United States—until recently.

In the late 1940s and early 1950s, around 5,000 cases were reported annually in the U.S. Thanks to improved rat and flea control efforts in the 1950s, cases dramatically decreased. But, starting around 2008, numbers began climbing again. On March 27, 2025, the Centers for Disease Control and Prevention (CDC) issued an alert: "Clinicians Should Be on the Lookout for Murine Typhus." So what exactly should we be watching for?

What is Murine Typhus? Murine typhus is an infection caused by a bacteria called Rickettsia typhi. It spreads through fleas that live on animals such as rats, opossums, cats, and dogs.

The bacteria is named after Howard Ricketts, who pioneered research on similar diseases like Rocky Mountain Spotted Fever.

People become infected when they come into contact with feces from infected fleas—either through:

• Scratches or broken skin

• Mucous membranes (eyes, nose, mouth)

• Inhaling dried flea waste

  
  

Those who frequently interact with feral cats and rodents face the highest risk of infection.

Symptoms to Watch For. Symptoms typically appear 7-14 days after infection. The most common sympoms include:

• Fever

• Headache

• Muscle pain

• Loss of appetite

• Nausea and vomiting

• Abdominal pain

• Cough

• Mental confusion

  
  

About half of patients develop a rash toward the end of the first week of illness. The rash usually starts on the trunk of the body and spreads outward but doesn't affect the palms or soles of the feet. The rash, however, varies greatly between patients and may not appear at all, making diagnosis challenging.

Treatment. The good news is that murine typhus responds well to treatment with the antibiotic doxycycline. For adults, the standard dose is 100 mg twice daily, while children under 100 pounds receive 2.2 mg/kg twice daily.

Treatment should begin as soon as murine typhus is suspected, without waiting for test results. While generally considered milder than other rickettsial diseases, most infected people still require hospitalization, and the disease has a 2% fatality rate among hospitalized patients.

The Comeback Story. The first U.S. case of murine typhus was identified in 1912. By 1931, there were 42,000 reported cases. After declining in the 1980s, national reporting requirements were dropped, though 16 states continued monitoring the disease.

Today, Texas, California, and Hawaii report the most cases. Since 2018, Texas has recorded about 600 cases annually, while California sees 150-200 cases each year.

Why the Resurgence? Dr. Lucas Blanton, an infectious diseases physician at the University of Texas in Galveston who has treated many murine typhus patients, notes: "It's not clear what's causing the rise in cases."

Increased awareness in states like Texas and California might be contributing to better detection and treatment. Climate change is also likely playing a role, as warmer temperatures generally benefit the fleas that carry this disease.