The Centers for Disease Control and Prevention (CDC) issued a Health Alert Network (HAN) Health Advisory on Friday, December 8, 2023 to inform healthcare providers and the public about an outbreak of Rocky Mountain spotted fever (RMSF) among people in the United States with recent travel to or residence in the city of Tecate, state of Baja California, Mexico. As of December 8, 2023, five patients have been diagnosed with confirmed RMSF since July 2023. All patients had been present in Tecate within 2 weeks of illness onset and presented to hospitals in southern California for treatment. RMSF is a serious, rapidly progressive disease transmitted by the bite of infected ticks. It is endemic in multiple states in Northern Mexico and areas of the southwestern United States. Doxycycline is the primary treatment for all patients and should be administered as early as possible. Providers who suspect RMSF should consider initiating doxycycline based on presumptive clinical and epidemiologic findings and not delay treatment pending the result of a confirmatory laboratory test. Cases left untreated or where treatment is delayed are often fatal. To date in 2023, the DC Department of Health has reported one probable, non-fatal case of RMSF.