An outbreak of Rocky Mountain spotted fever (RMSF) in southern California has raised concerns about the potential for disease-carrying ticks to enter the country through porous borders, according to Dr. Marc Siegel, clinical professor of medicine at NYU Langone Medical Center and a Fox News medical contributor. The Centers for Disease Control and Prevention (CDC) issued a health advisory on December 8, reporting three deaths and a total of five reported cases of RMSF. All five patients had recently traveled to or lived in the city of Tecate in Mexico, with three of them being residents of the U.S. and two being residents of Mexico. The patients were diagnosed in southern California hospitals between July and December 2023. In Mexico, the fatality rate for RMSF can be greater than 40% and the disease is five times deadlier for young children under the age of 10 compared to adults, according to the CDC advisory.

RMSF is a severe and often deadly disease transmitted by the bite of infected ticks. The bacteria that cause the disease, Rickettsia rickettsii, are spread by brown dog ticks, which are reddish brown and often found on domestic canines. Unlike Lyme disease, which is transmitted by deer ticks, the dog tick is larger and lacks the characteristic white spot. Symptoms of RMSF include headache, low-to-moderate fever, abdominal pain, rash, gastrointestinal symptoms, muscle aches and pain, and swelling. However, not everyone develops the classic “spotted” rash within the first few days, making the disease easily missed or misdiagnosed. Advanced symptoms can include mental disorientation, coma, swelling in the brain, organ damage, death of body tissue, and a decline in respiratory function. The disease can progress quickly and is often fatal if not treated early with the antibiotic doxycycline.

The CDC is urging health care providers to consider RMSF when evaluating patients with fever who have recently been in northern Mexico. They also recommend that all cases of RMSF be reported to local, state, territorial, or tribal health departments. For people experiencing symptoms and who have recently traveled to a northern Mexico city, immediate medical attention is recommended. To prevent the tick-borne disease, the CDC advises treating dogs with an EPA-registered insect repellent, wearing long sleeves and long pants, and checking for ticks after outdoor activities. If a tick is found, it should be removed right away.

The recent outbreak of RMSF in southern California has prompted the CDC to issue a level 1 travel advisory for Baja California, Mexico, where the disease has been found along with other Mexican states such as Sonora, Chihuahua, Coahuila, and Nuevo Le??n. The advisory urges travelers who develop symptoms of RMSF during travel or within two weeks of returning to the U.S. to seek medical attention. Symptoms of RMSF include fever, headache, and rash, which can develop two to four days after the onset of symptoms. Children under 10 years of age are five times more likely to die from RMSF.

San Diego County Public Health Services reported a death of a San Diego resident who had traveled to Baja California and contracted RMSF, highlighting the potential risks for travelers. The disease can be fatal if not treated early, and the antibiotic doxycycline is the standard treatment. The CDC emphasizes the importance of early detection and treatment to prevent the progression of the disease.