Rocky Mountain Spotted Fever Outbreak Sparks CDC Warning

Five people in California contracted the potentially deadly tick-borne illness while in Tecate, Mexico. All five individuals were hospitalized, and three died.

On December 8, the Centers for Disease Control and Prevention (CDC) issued a health advisory alerting healthcare providers and the public of a deadly Rocky Mountain spotted fever outbreak in California.

Between July and December of this year, the CDC says five people became ill with the disease within two weeks after traveling to or living in the city of Tecate, state of Baja California, Mexico. Three individuals died as a result.


Rocky Mountain spotted fever is endemic in Tecate and other border states in northern Mexico — meaning it occurs regularly in those geographical regions.

However, this tick-borne disease is also found throughout the United States, with more than 50% of cases occurring in Missouri, Arkansas, North Carolina, Virginia, and Tennessee.

The disease can progress rapidly and has a high fatality rate if not treated promptly with antibiotics. The CDC reports that in Mexico, the fatality rate can be more than 40%.

The agency urges healthcare providers to watch for patients exhibiting Rocky Mountain spotted fever symptoms, particularly if the person has recently visited or lived in northern Mexico. The CDC also says doctors should immediately begin treatment with doxycycline if a person has symptoms.

In addition, people who have traveled to Tecate or other areas in northern Mexico should seek medical attention if they develop a fever, rash, or headache within two weeks of returning home.

What is Rocky Mountain spotted fever?

Rocky Mountain spotted fever is a potentially fatal disease caused by the bacteria Rickettsia rickettsia, which transmits to humans through the bite of an infected American dog tick, Rocky Mountain wood tick, or brown dog tick. A person can also contract the disease when smashing ticks with bare fingers.

Symptoms of Rocky Mountain spotted fever typically develop two to 14 days after the tick bite and include:

  • Fever
  • Headache
  • Nausea and vomiting
  • Muscle pain
  • Reduced appetite

Another sign of the disease is a skin rash, which generally happens two to four days after the fever starts. The rash can vary from tiny dots to red splotches and begins on the wrists and ankles before spreading to the rest of the body. Still, some individuals with the illness don't develop a rash.

Diagnosing Rocky Mountain spotted fever involves blood tests, which can take weeks to produce results. Therefore, because the illness can be deadly, health experts say doctors should not wait for test results and begin treating anyone suspected of having the disease with the antibiotic doxycycline.

If left untreated, Rocky Mountain spotted fever has a 13 to 25% mortality rate.

How to prevent Rocky Mountain spotted fever

To help prevent this and other potentially fatal tick-borne illnesses, people should treat their clothing with insect repellents that contain DEET, picaridin, IR3535, para-menthane-diol (PMD), Oil of Lemon Eucalyptus (OLE), or 2-undecanone when venturing outdoors where ticks inhabit, like wooded, brushy, or grassy areas.

Also, before entering the house after being outside, a person should carefully check their clothing and body for ticks. In addition, people should regularly check any pets that are allowed to roam outdoors.

Rocky Mountain spotted fever isn't the only disease a person can acquire from a tick bite. For example, Lyme disease, Heartland virus, anaplasmosis, babesiosis, and alpha-gal syndrome — a meat allergy — are other common or emerging tick-borne conditions.


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