LOS ANGELES -- Rocky Mountain spotted fever (RMSF) continues to emerge in the California-Mexico border region, said the US Centers for Disease Control and Prevention (CDC), urging increasing awareness on both sides of the border to facilitate earlier diagnosis and appropriate treatment.

RMSF is a tickborne disease endemic in areas of the Americas. Persistent high incidence of the disease exists in northern Mexico, perpetuated by local populations of brown dog ticks and free-roaming dogs, according to CDC.

During July 2023 and January 2024, six cases of RMSF in persons with exposure in Tecate, Mexico were reported to the California Department of Public Health. Among them, three patients died.

This outbreak highlights a newly recognized location in Baja California with high RMSF risk, said CDC.

The serious nature of the disease and delays in initiating appropriate treatment can result in life-threatening consequences. Epidemiologic collaborations among local, state, federal, and international public health agencies were essential to identifying Tecate as the location of exposure, said CDC.

The agency called for increased health care provider awareness on both sides of the border to facilitate earlier diagnosis and initiation of appropriate treatment.