Colombia has declared a nationwide health emergency following a sudden and deadly outbreak of yellow fever, with at least 34 deaths and 74 confirmed cases reported so far in 2025, according to official Colombian health authorities (BBC; Reuters). The government’s urgent response underscores growing alarm about the re-emergence of this mosquito-borne virus in a region that had seen virtually no cases in recent years—a trend that should serve as a wake-up call for countries like Thailand, also home to mosquito-borne diseases.
Yellow fever is caused by a virus transmitted primarily by the Aedes and Haemagogus mosquitoes. It’s notable for symptoms that can range from mild fever and muscle aches to, in severe cases, jaundice, bleeding, and multi-organ failure. Mortality rates in this outbreak have hovered around 50% for those who enter the most severe “toxic” phase, Colombian Health Minister Guillermo Alfonso Jaramillo explained (BBC). The surge in cases comes ahead of the busy Easter holiday, typically a period of heavy domestic travel, especially to scenic coffee plantation areas like Tolima, the current epicenter of the outbreak.
This swift escalation is alarming for several reasons. First, Colombia had almost eradicated yellow fever: according to their Ministry of Health, there were only two cases in 2023, and none reported from 2019 through 2022 (BBC). Now, dozens have died in just a few months—a shift health officials attribute to increased mosquito activity and possible gaps in vaccine coverage. Colombians traveling to high-risk areas for Easter are now required to show proof of vaccination, and authorities are urgently campaigning for broader uptake, reminding citizens that the yellow fever vaccine is both safe and free (Economic Times Health). President Gustavo Petro warned: “People who have not been vaccinated should not go to high-risk areas during Easter: for now, the coffee area.”
What makes yellow fever especially insidious is that its early symptoms—fever, muscle pain, headache, loss of appetite—can mimic those of dengue, Zika, or other viral infections prevalent in tropical regions, including Thailand. Most patients recover after this initial phase, but according to the World Health Organization (WHO), about 15% develop severe complications. Of these, half “usually die within 10 to 14 days” (WHO Yellow Fever Fact Sheet). Diagnosis is further complicated in regions with limited laboratory access or where multiple mosquito-borne diseases circulate simultaneously.
International health experts like Dr. Ana P. Silva, an infectious disease specialist at the Pan American Health Organization (PAHO), highlight the cyclical threat posed by yellow fever. “Every time vaccination coverage drops, or the vector population surges, we see outbreaks return—even in areas thought to be under control,” Dr. Silva explains (PubMed: Yellow Fever Global Impact). Current research underscores the importance of integrated vector management—controlling mosquitoes through environmental measures and public education—alongside vaccination: “Yellow fever’s re-emergence underlines gaps in surveillance, prevention, and outbreak response that can affect any tropical or subtropical country,” notes a 2024 epidemiology study in Latin America (PubMed: Acute Undifferentiated Febrile Illnesses).
While Thailand does not have locally transmitted yellow fever, the vectors—primarily Aedes mosquitoes—are the same as those behind dengue, Zika, and chikungunya, all endemic here. Furthermore, Thailand is a regional travel hub: as international travel rebounds, imported yellow fever cases could theoretically appear, particularly among unvaccinated travelers returning from endemic areas in Africa or South America (Thai National Immunization Program Guidelines). The Thai Ministry of Public Health currently requires proof of yellow fever vaccination for travelers arriving from countries where the disease is endemic, but outbreaks elsewhere remind us of the continued need for vigilance.
Historically, Thailand’s battle is with dengue, not yellow fever, but the lessons are parallel. Rapid, unexpected outbreaks often strike hardest when vaccination complacency sets in or mosquito control efforts lapse—a reality reflected in periodic spikes in Thai dengue cases, especially in urban centres like Bangkok and in northern provinces during the rainy season (Bangkok Post, Dengue Surveillance). The current outbreak in Colombia prompts uncomfortable questions: are we ready for a viral “surprise” transmitted by our own ubiquitous mosquitoes? Do all at-risk communities have access to vaccination, and are public health professionals equipped with the resources to diagnose and act fast?
One emerging challenge identified by researchers is diagnostic confusion: a Colombian protocol for monitoring acute undifferentiated febrile illnesses (AUFI), now being studied across Latin America, shows that outbreaks may be missed or misdiagnosed without robust lab networks (PubMed: Epidemiology Protocol). Thailand’s Disease Control Department has invested heavily in disease surveillance, but ongoing investment in rapid diagnostics—and community education focused on recognizing symptoms and seeking early care—remains crucial.
An additional cause for concern is vaccine supply and logistics. During past outbreaks, yellow fever vaccine shortages complicated containment efforts. Although current stocks suffice in Colombia, a 2024 study in The Lancet advocates for new-generation vaccines with better production scalability (PubMed: Next-Gen Yellow Fever Vaccine). Thailand’s vaccine system, centralised but reliant on global supply chains for imported vaccines, might face similar bottlenecks should yellow fever ever become a risk for Thai travelers or residents.
For Thais, this story reinforces several practical recommendations. First, anyone traveling to yellow fever-endemic countries should receive a yellow fever vaccination at least 10 days before departure. The vaccine remains the gold standard, conferring lifelong immunity in most recipients (WHO Fact Sheet). Second, mosquito-borne disease prevention basics cannot be overemphasized: use DEET-based repellents, sleep in screened or air-conditioned rooms, and eliminate standing water around homes. Finally, heightened awareness about all fevers during mosquito season can help prevent complications from misdiagnosis, especially for vulnerable populations like young children and the elderly.
The Colombian health emergency is a vivid reminder of the unpredictable and persistent threat posed by mosquito-borne diseases. In a globalized era, no country can afford to be complacent. For Thai society, attentive surveillance, strong vaccination programs, and ongoing public education—in both English and Thai, for all communities—remain the keys to resilience. As Pha Thai, we must continue to say: ไม่ประมาท (mai pramat)—do not underestimate the power of prevention.
Sources:
- BBC: Colombia declares health emergency after dozens die
- Reuters: Colombia declares nationwide health emergency
- WHO Yellow Fever Fact Sheet
- Economic Times Health: Colombia declares emergency over yellow fever
- PubMed: Yellow Fever, Global Impact, and Prevention
- PubMed: Protocol Epidemiology of Febrile Illnesses
- Bangkok Post: Dengue Surges in Thailand
- Thai Ministry of Public Health