CDC issues warning for Rocky Mountain spotted fever near California-Mexico border

The Centers for Disease Control and Prevention issued a warning to residents for Rocky Mountain spotted fever after at least six people were infected at the California-Mexico border region over a six-month period last year.

Rocky Mountain spotted fever (RMSF) is a bacterial disease spread through the bite of an infected tick, according to the CDC.  It can occur during warm weather, but it most often occurs from April until September.

It's not spread from person to person, health officials said.

The CDC noted that five of six patients identified with RMSF in California during the period of July 2023 to January 2024 initially presented with non-specific clinical signs that could have contributed to incorrect diagnoses and inappropriate or delayed treatment.

Three of six patients died. All six cases of RMSF occurred in people with exposure in Tecate, Mexico.

Six confirmed RMSF cases identified within six months indicate a marked increase in California, where there are typically three confirmed cases or fewer reported each year, the CDC noted.

Brown dog tick-transmitted RMSF has been on the rise along the U.S.-Mexico border region.

Early signs and symptoms are not specific to RMSF (including fever and headache). However, the disease can rapidly progress to a serious and life-threatening illness.

Signs and symptoms can include:

• Fever (103° – 105°F)
• Headache
• Rash (Usually develops 2 to 4 days after fever begins)
• Nausea or vomiting
• Stomach pain
• Muscle pain
• Lack of appetite

RMSF can be life-threatening. Early treatment with the antibiotic doxycycline can prevent death and severe illness, health officials said.

While there is no vaccine for RMSF, Johns Hopkins Medicine shared tips to help prevent infection:

Wearing protective clothing, ticks can't bite through clothing, so dress in:

• Light-colored clothing, so you can spot ticks on clothing easier
• Long-sleeved shirts tucked into pants
• Socks and closed-toe shoes
• Long pants with legs tucked into socks

For more on RMSF, including more prevention tips, visit the CDC or Johns Hopkins websites.