July 18, 2024

CDC Warns of Deadly Tick-Borne Disease Outbreak Traced to Mexico

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Dec 11, 2023

The Centers for Disease Control and Prevention (CDC) has issued an alert regarding an outbreak of Rocky Mountain spotted fever (RMSF), a dangerous tick-borne disease, connected to recent travel to northern Mexico. At least three people have died and several more hospitalized in California due to the disease.

Recent Outbreak in California

According to the CDC alert, public health authorities in California are currently investigating five cases of severe RMSF with recent travel to Tecate, Mexico. Tecate is a city in the Mexican state of Baja California, located near the U.S. border.

Three of the RMSF cases have resulted in deaths so far. Two of the remaining patients have been hospitalized with serious illness. Symptom onset occurred between late November 2022 and early December 2022, indicating this is an emerging outbreak.

Case Details
Total Cases 5
Deaths 3
Hospitalizations 2
Location California, USA
Recent Travel History Tecate, Baja California, Mexico
Onset Range Late November 2022 – Early December 2022

This table summarizes key details on the initial cases that prompted the CDC warning. Additional cases with connections to Mexico may still emerge.

Rocky Mountain Spotted Fever Background

RMSF is caused by the bacteria Rickettsia rickettsii and transmitted through the bite of infected ticks. In the U.S., the main carrier ticks are American dog ticks and Rocky Mountain wood ticks.

Once infected, RMSF symptoms usually appear within 2 to 14 days. Early signs and symptoms include:

  • Fever
  • Severe headache
  • Muscle pain
  • Nausea & vomiting
  • Lack of appetite

A few days later, a red spotted rash typically emerges on the hands and feet, then spreads to the rest of the body. Without prompt antibiotic treatment, RMSF can rapidly become life-threatening.

On average, there are about 6 cases of RMSF per million people each year in the U.S. But Northern Mexico has recently seen much higher infection rates nearing 50-100 cases per million population per year in recent studies.

This elevated incidence of RMSF in communities near the U.S.-Mexico border poses a health risk for international travelers.

CDC Recommendations for Travelers

Due to this outbreak, the CDC has issued a Level 1 Travel Notice for Americans visiting Baja California state. This urges travelers to take enhanced precautions against RMSF.

Recommendations when visiting RMSF hotspots like Northern Mexico include:

  • Avoiding tick habitats like grassy or wooded areas
  • Using EPA approved insect repellants
  • Wearing long pants and sleeves outdoors
  • Checking clothing and skin carefully for ticks
  • Showering soon after being outdoors

If RMSF symptoms emerge within 2 weeks after traveling, promptly seek medical care and inform doctors about recent Mexico travel. Diagnosis relies on clinical suspicion and specialized laboratory blood tests.

The antibiotic doxycycline is highly effective at treating RMSF, especially when started early, but delay can lead to increased disease severity and death. Supportive hospital care is often required in severe RMSF cases.

The CDC also advises travelers to monitor pets that joined them in Mexico for tick-borne illness, and speak to a veterinarian if they seem sick after returning home.

Ongoing Investigations in Mexico

U.S and Mexican public health authorities are collaborating closely on field investigations around the suspected RMSF exposure hotspots near Tecate, Mexico.

The outbreak team is searching for additional RMSF cases in local hospitals and clinics in Mexico to better define the scope, risk factors, and transmission dynamics. They will also trap small mammals and ticks in the region to test for Rickettsia rickettsii and identify carrier species.

Research suggests ticks in the Amblyomma genus may be responsible for spreading RMSF in Mexico. Further genetic analysis can confirm if the bacteria samples match between ticks, animals, and human cases.

Unusually warm, rainy weather this year may have increased tick activity and RMSF risk around Tecate. But this requires more climatic modeling to substantiate.

Ongoing surveillance and data analysis aims to pinpoint specific Mexico locations and activities leading to the highest RMSF hazards. This intelligence can strengthen prevention guidelines for people traveling across the border.

Implications and Future Concerns

This CDC warning comes on the heels of Mexico declaring a national epidemiological emergency in August 2022 in response to rising RMSF cases countrywide. Over 5,400 total cases and 448 deaths were recorded in Mexico last year.

The infection pattern also seems to be worsening on the U.S. side – with 230 total reported domestic RMSF cases in 2022, representing an 18% increase from 2021. Rising temperatures associated with climate change may expand habitats for RMSF-carrying ticks further north.

Researchers also worry about additional tick-borne diseases like Lyme disease crossing into the U.S. from Mexico more frequently. The likelihood of transmitting novel viruses is also possible during these tick exposures.

Enhanced surveillance networks and quicker data sharing between countries can help identify and characterize emerging disease threats along the border to mitigate impacts. Traveler education is equally vital so those visiting RMSF hot zones take proper precautions.

As investigations continue tracing the origins of this RMSF outbreak, U.S. and Mexican health agencies hope honing prevention strategies targeting high-risk areas can help reverse the upwards disease trajectory in years to come. But it will require concerted binational efforts and flexibility adapting to shifting tick ecologies in a changing climate.


Centers for Disease Control and Prevention (CDC). (2023). Severe and fatal confirmed Rocky Mountain spotted fever (RMSF) among people with recent travel to Tecate, Mexico — Baja California, Mexico, 2022.

Medriva. (2023). CDC Alert: Outbreak of Rocky Mountain Spotted Fever in Tecate, Mexico.

NBC News. (2023). CDC cautions travelers to Mexico about Rocky Mountain spotted fever.

Forbes. (2023). CDC Issues Rocky Mountain Spotted Fever Alert: Here’s What To Know.

The Hill. (2023). CDC issues travel advisory for Rocky Mountain spotted fever in Mexico.




AiBot scans breaking news and distills multiple news articles into a concise, easy-to-understand summary which reads just like a news story, saving users time while keeping them well-informed.

To err is human, but AI does it too. Whilst factual data is used in the production of these articles, the content is written entirely by AI. Double check any facts you intend to rely on with another source.

By AiBot

AiBot scans breaking news and distills multiple news articles into a concise, easy-to-understand summary which reads just like a news story, saving users time while keeping them well-informed.

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