CDC issues health advisory after tick-borne illness causes 3 deaths in Southern California

By Stephanie Srakocic | Fact-checked by Davi Sherman
Published April 18, 2024

Key Takeaways

  • Five people have contracted the tick-borne Rocky Mountain Spotted Fever (RMSF) since July 2023.

  • The CDC is advising physicians to start any patients suspected of having RMSF on antibiotics immediately without waiting for lab results to confirm a diagnosis.

On December 8, 2023, the Centers for Disease Control and Prevention (CDC) issued a health advisory about a Rocky Mountain Spotted Fever (RMSF) outbreak. The outbreak is occurring in Baja California, Mexico, and in multiple border states in northern Mexico, with patients presenting to hospitals in southern California.[]

Since July 2023, five people have been affected, and three have died. All five had traveled to the border city of Tecate within two weeks of developing RMSF.[] 

RMSF is endemic in several border states in northern Mexico, including but not limited to Baja California, Sonora, Chihuahua, Coahuila, and Nuevo León. Unlike other tick-borne illnesses typically associated with wooded or open areas, RMSF is primarily transmitted in urban and suburban areas. RMSF is spread by brown dog ticks that often feed on domestic dogs.[] 

In Mexico, the fatality rate of RMSF can exceed 40%. The illness is fatal within days of infection, and half of all people who die from RMSF die within eight days of onset.

The antibiotic doxycycline can effectively treat RMSF when started early. The CDC recommends that any patients suspected of having RMSF receive doxycycline immediately without waiting for laboratory confirmation of a diagnosis. 

Early symptoms of RMSF can be‌ nonspecific and relatively mild, making them easy to mistake for flu or common cold symptoms. For instance, many people experience headaches, low to moderate fever, muscle and abdominal pain, and GI problems. A rash or spots on the back of the hands, wrists, ankles, and arms is a more distinct symptom that can help diagnose RMSF, but not everyone develops this symptom; when it does develop, it tends to do so later in the disease course.[] 

“Patients often present for care within the first two days because they start feeling very ill. So physicians are often seeing these very nonspecific symptoms, such as headache, fever, and muscle ache,” says family medicine specialist Allen Drexler, MD. “The ‘spotted’ part of Rocky Mountain Spotted Fever refers to a rash [that] is present in roughly 90% of cases at some point during the course of [a patient’s] illness. However, less than half of patients will have that rash in the first three days of their illness when they come in for care.”  

Untreated, RMSF spreads to the brain and can cause organ failure, breathing trouble, nervous system damage, and coma. Children under 10 are five times more likely than adults to die from RMSF. Four of the five patients infected in the current outbreak were under 18.[]

The CDC advises physicians to consider RMSF as a diagnosis for patients presenting with RMSF symptoms, especially if they’ve been to northern Mexico within the past two weeks. Physicians are advised to ask patients about travel history and possible exposure to ticks or tick-infested dogs. Treatment with doxycycline should be started immediately if RMSF is suspected, and all cases should be reported to local, state, territorial, or tribal health departments.[]

2023 travel and other risks to know about

As of December 2023, these include:

  • Mpox in the Democratic Republic of the Congo (DRC). The CDC advises enhanced precautions for anyone who travels to the DRC to prevent the spread of Mpox, a disease caused by infection with monkeypox virus. Mpox is endemic throughout West and Central Africa near forests and is transmissible via person-to-person contact, including in healthcare settings, shared living spaces, and sexual contact. [] 

  • Chikungunya in Timor-Leste. The CDC advises enhanced precautions for anyone traveling to Timor-Leste due to Chikungunya, a virus spread through mosquito bites .[] 

  • Diphtheria in Vietnam, Niger, and Guinea. The CDC is advising enhanced precautions, including up-to-date diphtheria vaccinations, for anyone traveling to Nigeria, Niger, and Guinea to prevent the spread of diphtheria. [] 

  • Crimean-Congo Hemorrhagic Fever in Afghanistan. Crimean-Congo Hemorrhagic Fever is a tick-borne illness. There aren’t any travel precautions in place, but the CDC advises that those who visit Afghanistan avoid contact with ticks and seek immediate medical care for any symptoms of illness. []  

  • Salmonella linked to cantaloupe. In January 2024, the CDC reported that 407 people across 38 states had fallen ill from salmonella linked to cantaloupe. Six people have died due to the outbreak. [] 

  • Salmonella linked to dog food. In November 2023, the CDC reported that seven people developed salmonella after handling contaminated dog food, dog bowls containing dog food, or saliva or poop of dogs that were fed contaminated dog food.[]

  • Salmonella linked to onions. In October 2023, the CDC reported that 80 people in 23 states developed salmonella after eating fresh diced onions. []

  • Listeria linked to fruit. Eleven people in seven states have developed listeria since November 2023 after consuming plums, peaches, and nectarines sold by HMC Farms.[]

  • Fungal meningitis linked to epidural anesthesia. The CDC is tracking reports—from January 1 to May 13, 2023—of fungal meningitis related to procedures using epidural anesthesia that were performed at two clinics in Matamoros, Mexico.[] 

  • Drug-resistant Pseudomonas aeruginosa linked to artificial tears. As of May 15, 2023, 81 patients in 18 states had developed drug-resistant Pseudomonas aeruginosa after using EzriCare Artificial Tears.[]

  • Norovirus linked to raw oysters. After reports of illness in the summer of 2023, the CDC and the US Food and Drug Administration advise restaurants, retailers, and consumers to avoid specific shipments of oysters that might be contaminated with norovirus.[]

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