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CRISIS OVERVIEW
Yellow fever is endemic throughout most of Colombia, except for high-altitude areas in the Andean region (INS 25/01/2023). This makes the emergence of the disease in the region remarkable. Tolima department is in the centre-west of the Andean region, 700m above sea level on average, and is divided into two main geographical zones: one flat zone near the Magdalena River Basin and one hillside zone near the eastern ranges (Camporigen accessed 25/01/2025). Although it is not surrounded by other departments that have reported cases in recent years, Tolima reported in October 2024 its first case of yellow fever since sanitary authorities began monitoring the disease in 2000 (INS 07/2024). Within the month, yellow fever cases were reported across rural Cunday, Prado, Purificación, and Villarrica municipalities of Tolima (MinSalud 02/11/2024; INS 27/12/2024). Increased seasonal rainfall in the department since October has created favourable breeding conditions for mosquitoes, increasing the risk of yellow fever transmission. The outbreak was declared on 7 November after the confirmation of eight cases; by the end of December, there were 12 confirmed cases (MinSalud 07/11/2024). Prior to this outbreak, red and orange intense rainfall alerts had been raised for several municipalities, including three of the four affected by yellow fever (Cortolima 08/10/2024). Stagnant water accumulating near residential areas located at lower elevations (between 300–800m above sea level) in most affected municipalities (Cunday, Prado, Purificación, and Villarrica) provides ideal breeding sites for the mosquitoes that transmit yellow fever (Ecos del Combeima 20/11/2024; Convertino et al. 25/10/2023; Gobernación del Tolima 23/11/2020).
By September, Colombia accounted for 17 of all 50 yellow fever cases and 9 of the 24 related fatalities reported in Latin America during 2024 (OPS 06/11/2024; INS 31/10/2024). On 23 October, Tolima recorded its first case of yellow fever in Villarrica (El Olfato 23/10/2024). By the end of the month, one person was hospitalised for the disease, although by late November 2024, no hospitalisations were reported in the department. The low hospitalisation rate could be because of the concentration of cases in remote villages (INS 03/11/2024). Authorities declared a public emergency throughout the department on 21 November (INS 28/11/2024 and 29/10/2024; Secretaría de Salud del Tolima 21/11/2024).
The outbreak has primarily affected rural areas of Cunday, Prado, Purificación, and Villarrica, with no reported cases in urban areas. All the affected municipalities border the natural park Bosque de Galilea, which has been exposed to extensive deforestation based on registers taken between 2000–2025, especially near Cunday municipality, where 5.14kha has been deforested (INS 28/11/2024 and 27/12/2024; Global Forest Watch accessed 25/01/2025).
Of the 12 confirmed cases by late November 2024, nine were men, and three were women. Sanitary authorities in Tolima have no exact disaggregated information about the number of vaccinated people in the department. From estimations of the vaccination rate among infected people countrywide, it is possible that only 9% of registered cases (one or two people) have been vaccinated (INS 31/12/2024). Across Colombia, the most affected groups have been male agricultural workers and rural students of all genders, likely exposed in high- risk areas such as wild forest zones (OPS 06/11/2024). The combination of environmental conditions favourable for vector breeding, heightened rainfall, warm temperatures, and the presence of non-human primates in sylvatic environments significantly compounds the potential for a yellow fever outbreak in the department.
Although the authorities have declared the end of the emergency outbreak in Tolima in December 2024, the forthcoming rainy season, typically from January–April, alongside the seasonal mobility of agricultural workers in the rice sowing season during the same period, may increase the incidence of yellow fever. The movement of people within rural areas and between rural and urban areas can significantly influence disease transmission (MinSalud 08/08/2018). The increased presence of workers in rural areas where the virus circulates from wild animals through mosquitoes elevates the risk of exposure and infection (RCN 02/12/2024; IRI accessed 13/01/2025; WMO accessed 13/01/2025; MinSalud 08/08/2018).
Like yellow fever, dengue is a vector-borne disease transmitted by the same type of mosquito. Chemical control methods of Aedes aegypti, the main vector spreading yellow fever and dengue, have intensified in Colombia in recent years. In 2023, there were almost 131,000 reported cases of dengue, double the number of reported cases in 2022 (68,000) (Universidad del Rosario 27/05/2024). In the department of Tolima, chemical control methods have focused on rural and urban municipalities affected by dengue; a specific chemical control approach for the yellow fever outbreak has not been reported (Gobernación del Tolima 13/03/2024).
Health authorities have implemented community and biological control methods since the beginning of the emergency in October 2024 (ConsultorSalud 07/11/2024). In Tolima, the vaccination rate among the overall population is between 87–93% (MinSalud 11/07/2023; ConsultorSalud 07/11/2024). The vaccination rate among one-year-old babies is 87%, but the overall immunisation rate among adults is sharply lower at 54% (MinSalud accessed 20/12/2024; MinSalud 29/07/2024). The vaccination campaign is currently focused on villages in rural zones where cases have been identified and in urban sectors of the affected municipalities. By the second week of November, almost 10,000 people had been vaccinated in the affected areas, reaching an 80% immunisation rate. There are also community-based campaigns around cleaning stagnant water and the use of mosquito repellent (Gobernación del Tolima 15/11/2024). At the same time, landslides have caused road blockades in eastern municipalities, particularly Prado (Cortolima 23/11/2024). These constraints, which are forecasted to persist until at least January 2025 given heavy rains, pose a significant risk to civilians by hindering access to healthcare facilities, impeding the delivery of medical supplies and vaccines, and restricting vaccination campaigns in remote rural areas (RCN 09/12/2024).
The surveillance of suspected cases of infection depends on the departmental laboratories that have the proper infrastructure for handling biological samples to confirm cases (MinSalud 14/08/2024). For Tolima department, the laboratory is in the capital city Ibagué, which is 150km away from the outbreak focus area (MinSalud 14/08/2024; Secretaría de Salud de Tolima accessed 25/01/2025). This centralised surveillance system is a barrier to prompt diagnosis in remote municipalities, potentially leading to significant underreporting. The authorities declared the outbreak to be controlled by December, with 142 potential infection events recorded between June–December 2024 in Tolima, but six more were reported in the first two weeks of 2025 (INS accessed 14/01/2025).
The mortality rate of the yellow fever outbreak in Tolima is notably high. Of the 12 reported cases, 5 resulted in death, representing a 42% fatality rate. This figure is significant compared with the 23% fatality rate throughout Colombia (INS 25/01/2023). All fatalities occurred in rural areas, specifically in the municipalities of Berlín and Puerto Lleras in Villarrica (three fatalities), Aguas Negras in Purificación (one fatality), and Montoso in Prado (one fatality) (Secretaria de Salud de Tolima 11/12/2024).