Reemergence of arboviruses in the Andean-Amazonian corridor: eco-epidemiological dynamics and surveillance in Colombia, Ecuador, and Venezuela

Re-emerging infectious diseases pose a growing threat to global public health, especially in tropical regions where environmental changes, rapid urbanization, declining vaccination coverage, and human mobility facilitate the transmission of various pathogens. Latin America is currently facing an unprecedented epidemiological crisis, with infectious diseases spreading amid conditions of inequality and fragmented health systems. The Andean-Amazonian corridor represents an epidemiological hotspot for various vector-borne diseases. The objective of this article was to analyze the epidemiological trends of re-emerging diseases in these countries from 2023 to 2026, identifying ecological, social, and health factors linked to their re-emergence. The results reveal a sustained increase in arboviruses such as dengue, chikungunya, and yellow fever, as well as the persistence of malaria in Amazonian areas. In Ecuador, 37,840 cases of dengue were reported in 2025, with 65 deaths, while in Colombia, an outbreak of yellow fever was recorded with 132 confirmed human cases from 2024 to 2025. The situation regarding yellow fever in Venezuela during 2025 and 2026 shows signs of reemergence within the regional context of South America, associated primarily with the circulation of the virus in sylvatic cycles and the risk of spread to neighboring areas. The findings indicate that the interaction between climate change, deforestation, migration, and evident weaknesses in epidemiological surveillance, vector control, limited access to health services, infodemic, poor health education, and vaccine hesitancy contribute to the reemergence. In conclusion, it is necessary to implement a One Health approach in Latin America, which is justified not by the number of reported cases, but by the magnitude of what remains undetected and unreported, as well as genomic surveillance to identify variants, trace transmissions, monitor drug resistance, and anticipate outbreaks, thereby transforming our understanding of complex, emerging, and often neglected diseases.

Emerging and re-emerging infectious diseases (EIDs), pose one of the greatest challenges to global public health. These diseases include those whose incidence has increased in recent decades or that have reappeared in regions where they had previously been brought under control. Factors such as climate change, globalization, deforestation, and human mobility have contributed to the geographic spread of pathogens and vectors (1).

Latin America is facing an unprecedented epidemiological situation, characterized by the emergence of new and re-emerging infectious diseases, such as dengue (DENV, transmitted primarily by Aedes aegypti), the Oropouche virus (OROV, transmitted by Culicoides paraensis), yellow fever (YFV), monkeypox (MPOX), chikungunya (CHIKV), Zika (ZIKV), and leishmaniasis, among others. These diseases spread in contexts of structural inequality, with a direct and significant impact on health systems and regional health response capacity. The most vulnerable populations include children under 15 years of age, older adults with comorbidities, pregnant women, as well as indigenous and rural communities (2).

The Andean and Amazonian regions of Ecuador, Colombia, and Venezuela constitute a global hotspot for emerging and re-emerging infectious diseases, driven by the convergence of climate change, accelerated deforestation, weak health and epidemiological surveillance systems, and the humanitarian crisis that is fueling migration. During the 2023 to 2026 period there has been an unprecedented increase in reported cases of arboviruses, parasitic diseases, re-emerging vaccine-preventable diseases, and zoonoses, many of which are influenced by the spread of vectors and limitations in vector control strategies.

The Andean-Amazonian Corridor region is characterized by ecological and climatic conditions favorable to the proliferation of vectors such as Aedes aegypti, Anopheles spp., sandflies, and ticks, facilitating the transmission of pathogens between animals and humans. This, combined with climatic, environmental, and urban factors that have contributed to the disease’s geographic spread, increases the risk of diseases (3, 4).

There is a highly complex epidemiological corridor in northwestern South America, comprising Ecuador, Colombia, and Venezuela, where the convergence of tropical ecosystems, demographic pressure, institutional crises, and climate change drives the emergence and re-emergence of infectious diseases with the potential for regional outbreaks, as has been reported. Because they share certain ecological, demographic, and social characteristics, these areas stand out as prime settings for the emergence and re-emergence of infectious diseases (5).

Certain characteristics such as tropical biodiversity and the vast Amazonian, Andean, and coastal ecosystems combined with high levels of internal and international population mobility, as well as socioeconomic and institutional crises, weaken health systems and create a mosaic of significant epidemiological risk (6, 7).

The Andean-Amazonian region of South America comprising the tropical and subtropical areas of Ecuador, Colombia, and Venezuela represents one of the most complex epidemiological settings. This subregion shares ecological characteristics that are unique: the altitudinal transition from the inter-Andean valleys (1,500–3,500 m a.s.l.) to the Amazonian lowlands (< 200 m a.s.l.) generates a diversity of ecosystems that favors the presence of various vectors, animal reservoirs, and pathogens (8).

A complex eco-bio-social interaction in which certain meteorological, climatic, and socioeconomic factors, together with the specific characteristics of the domestic environment, influence the abundance and distribution of the Aedes mosquito as a vector, and thus the risk of arbovirus transmission in Latin America (9).

In 2026, the situation regarding re-emerging diseases in Colombia, Ecuador, and Venezuela shows an increase in epidemiological events, particularly vector-borne diseases such as yellow fever, whose transmission remains active and is spreading to new geographic areas in South America. The Pan American Health Organization has warned of the persistence of cases since 2024, with reports in non-endemic areas and a risk of urban outbreaks, reflecting a shift in the regional epidemiological pattern. Furthermore, in 2025, hundreds of cases with high fatality rates were reported in countries such as Colombia, Ecuador, and Venezuela, with transmission continuing into 2026. In the first seven weeks of 2026, there were 25 cases and 13 deaths in Colombia, representing a case fatality rate of 53%, and in Venezuela, there were 6 cases and 1 death, for a case fatality rate of 17%. Another important finding was the reporting of 19 outbreaks in non-human primates that were not laboratory-confirmed. This situation is exacerbated by factors related to prevention, care, and response capacity within health systems, as well as social and environmental determinants. Venezuela is currently conducting emergency campaigns to control active outbreaks, with an emphasis on closing critical vaccination gaps in border and mining states, where the constant movement of people facilitates the spread to Colombia and Brazil (10, 11). Ecuador reported 11 cases and 8 deaths in 2025 (12), while Colombia is implementing national plans for the elimination of priority communicable diseases, highlighting the persistence of these diseases as a public health problem, while Colombia is implementing national plans to eliminate priority communicable diseases highlighting the persistence of these diseases as a regional public health problem it has intensified genomic surveillance to detect viral mutations and has prioritized vaccination in departments within the Orinoco and Amazon basins (13, 14).

EIDs have a significant impact by overburdening health systems, increasing morbidity and mortality, and disproportionately affecting populations considered vulnerable, thereby highlighting structural limitations in surveillance and epidemiological response (15). Recent research also highlights the reemergence of diseases such as yellow fever in the Andean region during 2024 and 2025, with outbreaks linked to low vaccination coverage, deforestation, and failures in integrated health approaches (“One Health”), underscoring the need to strengthen regional preparedness. In this context, projections for 2026 point to an increased risk of new viral epidemics, necessitating the consolidation of genomic surveillance systems, intersectoral strategies, and sustainable policies to anticipate and mitigate the spread of such events (16).

Given the above, it is important to analyze the cause-and-effect relationship between the spread of pathogens and structural fractures in the region. By cross-referencing the accuracy of the data with the realities of the most vulnerable populations, it is essential to identify the underlying factors to combat the invisibility of outbreaks and provide a scientific basis that drives the design of urgent, equitable, and preventive public policies under a One Health approach.

A narrative review of the scientific literature was conducted to analyze the epidemiological patterns of emerging and re-emerging arboviral diseases in the Andean and Amazonian regions of Ecuador, Colombia, and Venezuela during the period from January 2023 to April 2026. This narrative approach seeks to critically integrate and synthesize the available evidence without being restricted to the formal procedures of a systematic review, which is appropriate given the heterogeneity of the sources and the exploratory nature of the topic.

Databases consulted

The literature search was conducted in the following databases: PubMed/MEDLINE, Scopus, Web of Science, LILACS (Latin American and Caribbean Health Sciences Literature), and SciELO (Scientific Electronic Library Online). Additionally, the official repositories of the Pan American Health Organization (PAHO/WHO), the Centers for Disease Control and Prevention (CDC), and the national epidemiological bulletins of the ministries of health of Ecuador, Colombia, and Venezuela were consulted.

Search strategy and Boolean operators

Terms in Spanish and English were used in combination with the Boolean operators AND, OR, and NOT. The search strategy was structured as follows:

(dengue OR chikungunya OR Zika OR “yellow fever” OR Oropouche OR arbovirus OR “yellow fever” OR DENV OR CHIKV OR ZIKV OR OROV) AND (“América Latina” OR “Latinoamérica” OR Ecuador OR Colombia OR Venezuela OR “Andean region” OR “Amazon region” OR ‘Amazonia’ OR “Andes”) AND (“emerging diseases” OR “re-emerging diseases” OR “emerging infectious diseases” OR “re-emerging diseases” OR “vector-borne diseases” OR “diseases transmitted by vectors”) AND (“Aedes aegypti” OR “Aedes albopictus” OR “Culicoides paraensis” OR mosquito OR vector OR arbovector) AND (epidemiology OR surveillance OR “epidemiological surveillance” OR ‘outbreak’ OR incidence OR “disease burden”) NOT (malaria OR “Plasmodium” OR “Chagas disease” OR leishmaniasis).

Search period

The search focused on publications from January 2023 to March 2026. Additionally, references published prior to this period were included when they were essential for contextualizing historical, ecological, or conceptual aspects relevant to understanding the phenomenon under study.

Inclusion criteria

The following were included:

Original articles, narrative and systematic reviews, and meta-analyses published in peer-reviewed scientific journals.

Reports, bulletins, and technical reports issued by international (PAHO, WHO, CDC) and national organizations.

Publications in Spanish, English, or Portuguese.

Studies with a geographic focus on Ecuador, Colombia, Venezuela, or the Andean and Amazonian regions of South America.

Publications available in full text.

Exclusion criteria

The following were excluded:

Conference abstracts, theses, and gray literature without formal scientific validation.

Articles without access to the full text.

Publications not related to arboviral diseases or the defined geographic scope.

Studies focused exclusively on non-arboviral diseases such as malaria, Chagas disease, or leishmaniasis.

Evidence synthesis

The retrieved evidence was analyzed, organized, and synthesized in a narrative and integrative manner by the authors. No statistical meta-analysis procedures were applied, nor was a systematic review protocol followed. The synthesis was structured around the main arboviruses studied, the eco-bio-social factors associated with their transmission, the epidemiological profile of the Andean and Amazonian regions of the three selected countries, and the One Health approach.

Epidemiological dynamics of dengue in Venezuela, Colombia, and Ecuador: a scenario of sustained transmission

Dengue is the most prevalent arbovirus disease in the Andean-Amazonian subregion. According to PAHO, in 2026, 745,736 suspected cases of dengue were reported in the Americas, with a cumulative incidence of 74 cases per 100,000 inhabitants. Likewise, in 2025, 1.68 million confirmed cases and 2,207 deaths were reported, with a case fatality rate of 0.05% (17). In the Andean sub region, the situation is critical; in Colombia, 2025 ended with 123,745 cases and an incidence of 370.7 per 100,000 inhabitants (18).

The dengue virus (DENV) is transmitted through the bite of Aedes aegypti and Aedes albopictus mosquitoes. which circulate in four serotypes (DENV-1 to DENV-4). The region reports hyperendemicity, with simultaneous outbreaks of dengue and the reemergence of other viruses (19). Table 1 shows the epidemiological dynamics of dengue in Venezuela, Colombia, and Ecuador.

A key point is that Colombia and Ecuador accounted for 1.7% and 0.9%, respectively, of the fatal cases recorded through early June 2024 (24). The Southern Cone reported 244% more cases than in the same period of 2023 and 422% more than the average for the past five years (25) For this reason, 2024 was a year of significant epidemiological impact, with the Region of the Americas recording more than 12.6 million cases and 7,713 deaths (26).

One of the most dynamic tropical epidemiological corridors in South America consists of Ecuador, Colombia, and Venezuela and is characterized by sustained transmission of Aedes aegypti, the simultaneous circulation of multiple viral serotypes, and a vulnerable population. Tropical and subtropical climatic conditions, combined with structural inequalities and weaknesses in health systems, have contributed to the persistence and spread of dengue in these countries (19).

Epidemiological studies conducted in Venezuela, Ecuador, and Colombia have shown that the increase in transmission is directly linked to structural factors such as rapid urbanization, high population mobility, and limitations in surveillance and vector control systems. In Ecuador, the rise in incidence has been directly linked to climate change, unplanned urbanization, and deficiencies in vector control (27). In addition, simultaneous circulation of multiple serotypes, increases the risk of severe disease and mortality (28). At the entomological level, the persistence and expansion of Aedes aegypti is closely linked to structural conditions that favor its reproduction, such as the availability of breeding sites, inadequate solid waste management, and difficulties in the supply of drinking water (29). Meanwhile, in Venezuela, viral phylogeography studies have shown that the collapse of the healthcare system and massive human mobility have raised growing concerns about the cross-border spread of infectious diseases.

In this regard, phylogenetic analyses in Ecuador revealed DENV originating from Venezuela and Colombia (30). In Colombia, the WHO (World Health Organization) notes that unplanned urbanization, insecticide resistance in vectors, and climate change are the most influential factors in the increased incidence of dengue, particularly the El Niño Southern Oscillation (ENSO) and increased rainfall, which have played a key role in the most recent epidemic cycles (29).

The epidemiological situation in Venezuela is complex; there has been a more than ninefold increase in dengue cases over the past 25 years, however, the latest official report from the Ministry of Health dates back to 2016, and there are no recent studies that epidemiologically characterize the infection or the circulating serotypes, making the country a blind spot in surveillance with the potential to export viral strains to neighboring countries. A study conducted in Miranda State revealed that 95% of cases were attributed to the DENV-3 serotype (31). It is of great importance to note that the reappearance of a serotype that has not circulated in the last decade, such as DENV-3, coupled with an increase in the susceptible population, raises the likelihood of severe dengue cases (32).

The year 2024 marked an unprecedented epidemiological milestone in the history of dengue in the Americas, redefining public health challenges and emerging trends in surveillance, vector control, and vaccination. By epidemiological week 12 of 2026, 624,085 suspected cases of dengue had been reported in the Region of the Americas, with a cumulative incidence of 62 cases per 100,000 inhabitants, a 64% decrease compared to the same period in 2025, and a 65% decrease compared to the average of the past five years. In the same epidemiological week in Ecuador, 6,139 cases were reported with circulation of DENV2 and DENV3; Colombia, meanwhile, recorded 27,675 cases, while Venezuela there are no official reports of cases (33).

The transmission dynamics of DENV are influenced by a complex interplay of sociodemographic determinants; among host factors, age, sex, and ethnicity or race stand out as critical variables that determine not only patterns of exposure to the vector but also immunological susceptibility and the severity of infection. One study reported that people of mixed race were more likely to develop dengue than other ethnic groups (34). Some studies have found no association between gender and DENV infection (35, 36), but the data vary. A study in the Amazon reported that DENV infection rates were higher among men than among women (37); however, a recent study showed evidence of age-modifying effects on vulnerability to dengue incidence resulting from an increase in average temperature and provides early indications of the possible role of geography and gender (38). Similarly, the distribution of dengue by gender in the Amazon and the Andes varies according to urban versus rural settings and age, although clear trends of greater vulnerability among women are observed in certain contexts in the Amazon and an alternation in the Andes (38, 39).

Age is a critical factor; in this regard, it has been found that children under 15 years of age constitute the group with the highest incidence, accounting for more than one-third of severe cases. In Colombia, the median age in a prospective cohort of 600 patients with dengue was 13 years, of whom 28% developed severe symptoms or a critical clinical course. During the 2023–2024 outbreak in Colombia, the disease predominantly affected children and adolescents; the independent risk factors for severe manifestations identified were not living in an urban area, the presence of edema and leukocytosis on admission, thrombocytopenia, and lymphopenia; however, infections caused by serotypes other than DENV-2 were less likely to be severe (40). At the subregional level, in 2023 the mortality rate in the Andean countries reached 8.8%, with more than 9,414 severe dengue cases representing 0.6% of all reported cases, and in 2024 the region recorded 11,400 severe cases with a mortality rate of 5.7% (24). Although the age group consisting of adults over 60 years of age has a lower absolute incidence, it exhibits the highest case-fatality rates. The presence of comorbidities such as diabetes, hypertension, and renal failure amplifies the risk of progression to severe dengue and shock (41), especially in Venezuela, where the collapse of the healthcare system prevents timely care. In settings with high transmission rates, this group has the highest age-specific mortality rate of all age groups. This age-based divide reveals two converging realities: on the one hand, older adults with compromised immune systems who also have chronic conditions that can turn a fever into a deadly cascade; and on the other, children especially those in areas lacking basic sanitation and with high mosquito populations who are repeatedly exposed and vulnerable to hemorrhagic forms of the disease (42).

Pregnant women constitute another critically vulnerable group, as DENV infection not only increases the risk of severe maternal complications and a higher risk of maternal bleeding due to the thrombocytopenia characteristic of the disease, but has also been associated with adverse neonatal outcomes, such as preterm birth and low birth weight (43, 44).

The accumulated scientific evidence highlights the urgent need to redirect public health resources and efforts toward modifiable risk factors, given that their persistence perpetuates cycles of transmission that the health systems of Ecuador, Colombia, and Venezuela are unable to fully manage. These factors stem from a combination of environmental, social, and institutional determinants that act synergistically; in Ecuador, ecological modeling and species distribution identified population size, a deficient waste collection system, altitude, and access to water as the factors most strongly associated with the presence of Aedes aegypti in urban and rural areas of the country, with medium- to high-risk areas distributed across ecologically diverse regions (45); However, at the provincial level, the main factors identified on the Ecuadorian coast were domestic water reservoirs, warm temperatures, humidity, and poor sanitary conditions, with Guayas, Manabí, and El Oro as the provinces with the highest historical incidence and 61,329 reported cases in 2024 (46). In Colombia, it was determined that DENV-2 infection and heterologous serotype reinfection were the most significant factors for the development of severe dengue (47); at the regional level, it was found that in Ecuador, Colombia, Venezuela, and Peru, rapid urbanization and a shortage of diagnostic resources hinder the timely detection of cases, compounded by a lack of health infrastructure, as well as a lack of awareness about the disease and deficiencies in prevention programs, which have facilitated the spread of dengue among vulnerable populations (48). In Venezuela, the absence of official data since 2016 prevents an analysis of risk factors based on systematic surveillance, but available independent studies indicate that community members in crisis contexts describe the risk of dengue as resulting from complex interactions between biophysical conditions, economic barriers to prevention, low risk perception, lack of social cohesion, absence of municipal services, drinking water, sanitation, and waste collection (49) factors that are structurally exacerbated by the collapse of the health system, the poverty of 86.9% of the population, and the mass displacement that characterizes the country’s humanitarian crisis.

In general, the challenges faced by countries in the region regarding dengue prevention and control share common features, such as Aedes aegypti resistance to insecticides, which has compromised the effectiveness of traditional vector control strategies, and genetic mutations as seen in Venezuela, where genetic mutations and high levels of enzymatic activity have reduced the efficacy of insecticides (50).

Thus, during the 2023–2026 period, drastic changes were observed, with the 2024 dengue epidemic in the Americas considered the largest on record has been recorded in epidemiological records as the year in which dengue exceeded all known limits, severely affecting all three countries despite their differences, hence the importance of vector control, waste management, health education, and timely care.

Beyond dengue: the silent spread of emerging arboviral diseases in the Andean region

Diseases transmitted by Aedes mosquitoes notably chikungunya, dengue, yellow fever, and Zika represent a growing global problem. While dengue is one of the fastest-growing infectious diseases worldwide, with between 100 and 400 million new infections each year (51), it is important to take the others into account as well. The arboviral situation in the three countries extends beyond individual viruses and constitutes a multiviral threat that requires simultaneous surveillance of at least three pathogens (OROV, ZKV, and YFV) with distinct epidemiological patterns, all of which are equally concerning.

Evidence indicates that certain viruses, such as Oropouche and yellow fever, continue to spread or reemerge in the region due to deforestation, unplanned urbanization, and significant gaps in epidemiological surveillance, thereby increasing the risk of vulnerable populations. In this regard, the recent resurgence of the Oropouche virus in South American countries during 2025 highlights limitations in the timely diagnosis of the infection and in reporting systems, leading to underreporting and silent spread. During the first 7 months of 2025, 12,786 cases were reported in the Americas, of which 26 were diagnosed in Colombia and 5 in Venezuela (52).

For decades, OROV was an endemic disease confined to the Brazilian Amazon, but it has now become a regional emergency of a new magnitude: as of February 2025, cases have been reported in humans and animals in 11 countries in the Americas, including Brazil, Peru, Ecuador, Colombia, and Venezuela, driven by the new OROVBR-2015–2024 lineage, which has established chains of sustained local transmission outside the Amazon basin (53), demonstrating the growing geographic spread of a virus transmitted primarily by the midge Culicoides paraensis (54). Even more alarming is the newly documented clinical profile: in 2024, vertical transmission of OROV was confirmed in cases of newborns with microcephaly, ventriculomegaly, agenesis of the corpus callosum, and joint malformations; a newborn with these congenital anomalies attributed to vertical transmission died at 47 days of age, and a subsequent study of 68 infants born with microcephaly of unknown cause identified OROV as the causative agent in cases previously negative for classic congenital pathogens (55).

This pattern is similar to Zika during 2015–2016, when vertical transmission caused a surge in microcephaly that had a major impact on public health in Brazil. This similarity is raising concerns among epidemiologists: if Oropouche follows the same trajectory, pregnant women especially those living near tropical forests or areas with high vector density will be at the highest risk. However, unlike Zika, there is no vaccine or specific treatment for Oropouche: only surveillance, vector control, and individual protection (56).

Oropouche fever is considered a neglected infectious disease because certain aspects related to its pathogenesis and transmission are not fully understood (54). Another important factor is that it shares symptoms with other arboviral diseases such as dengue, Zika, Chikungunya, and Mayaro fever, which makes diagnosis difficult (57).

Ecuador stands out among the countries with a history of OROV circulation, along with Brazil, French Guiana, Panama, Peru, and Trinidad and Tobago. In February 2024, PAHO issued an epidemiological alert due to the number of cases reported in the region, particularly in Brazil. An interesting finding is that the L and S segments of this virus form a monophyletic group with another sequence circulating in Ecuador in April 2024 (isolate PQ863772.1 from an Ecuadorian traveler), whose provincial origin is uncertain. Both sequences differ from the Ecuadorian OROV sequences previously detected in 2016 and from the OROV strain that drove the 2023–2025 epidemic in Brazil (58), suggesting that distinct variants exist within Ecuador, independent of epidemics in neighboring countries.

By August of that year, the global tally exceeded 10,000 cases, concentrated in Brazil, Bolivia, Colombia, and Peru. The number of cases in Brazil reached 7,497 confirmed cases as of August 6, 2024, with 78% concentrated in the Amazon region (59). For this reason, PAHO urged the strengthening of molecular surveillance for emerging arboviruses throughout the region (54).

The situation in Venezuela warrants particular attention from an epidemiological perspective, given that more than seven million Venezuelan migrants have passed through the Darien Corridor connecting Colombia and Panama, where Panama reported 14 cases in 2024 and 214 in 2025, raising the plausible hypothesis of an epidemiological link between the circulation of OROV in Venezuela, Colombia, and Ecuador and the Panamanian outbreaks, which requires verification through urgent genomic surveillance (60).

It is important to note that there is no vaccine or specific treatment for Oropouche: only surveillance, vector control, and individual protection. Therefore, it is necessary to understand the disease and identify potential environmental, socioeconomic, and demographic factors that influence the prediction, detection, and distribution of OROV cases. In this way, different disciplines can provide new methods and tools for the research and implementation of integrated surveillance mechanisms.

Other arboviruses, such as chikungunya and Zika, require public health attention; case counts are high in the Americas: 316,836 for chikungunya and 24,570 for Zika. Among the factors contributing to the increase and spread of these diseases are failures in mosquito control, rapid population growth, and changes in ecosystems (61). In Latin America, the incidence rate is linked to various socioeconomic conditions and social factors, where population growth in urban areas creates an environment conducive to the proliferation of the mosquito, a vector of dengue and the primary agent of the disease. This is compounded by migration, sedentary lifestyles, and internal displacement, which facilitate the entry and spread of dengue into new regions, especially when migrants come from areas with high incidence rates (62).

Other studies have shown that living in areas with high population turnover, primarily related to tourism, is a significant factor in exposure to the vector and the risk of infection with ZIKV, DENV (63), and CHIKV (64). High population density has also been shown to influence the spread of ZIKV and CHIKV (65).

The chikungunya virus (CHIKV, Togaviridae, Alphavirus) is an arbovirus transmitted by the Aedes aegypti and Aedes albopictus mosquitoes; clinically, it is characterized by a sudden onset of fever and severe polyarthralgia, which can progress to chronic, disabling arthritis in 30–60% of cases. In 2024, 431,417 cases and 245 deaths from chikungunya were reported in the Region of the Americas; in 2025, despite a decrease compared to 2024, outbreaks remained active in specific hotspots, with more than 97% of cases concentrated in South America (66). The situation took on a new epidemiological dimension beginning in late 2025: PAHO issued an epidemiological alert on February 11, 2026, in response to the sustained increase in cases and the resumption of local transmission in areas that had not recorded virus circulation for several years, noting that environmental factors such as extreme temperatures favor vector reproduction. From a virological perspective, genomic analysis in the Americas identifies the circulation of the ECSA genotype (East/Central/Southern Africa) without the E1-A226V mutation associated with increased transmissibility by A. albopictus, and the co-circulation of this genotype with the Asian genotype raises concerns about its potential adaptation and changes in transmission dynamics (67).

CHIKV continues to circulate endemically in the subregion. For the Americas in 2023, PAHO reported 27,397 cases of Zika (incidence of 3 per 100,000), a 22% increase over the five-year average, concentrated in Brazil (68). In recent years, Ecuador reported only one imported case of chikungunya in 2023 (67). However, this situation contrasts with the high volume of dengue recorded during the same years (61,352 cases in 2024), indicating that, despite the density of the Aedes aegypti vector in the coastal and Amazonian provinces, CHIKV has not managed to establish a sustained indigenous transmission cycle during this period. The absence of local circulation does not imply, however, an absence of risk, since the resurgence of transmission in neighboring countries such as Colombia, along with migratory flows and the high susceptibility of populations without prior immunity, creates a scenario of latent risk that requires active entomological surveillance and systematic differential diagnosis with dengue (69).

In Venezuela, there is a lack of data for the subregion, which makes it impossible to determine the actual burden of the virus in recent years; however, the country experienced a CHIKV epidemic in 2014–2015, concurrently with Colombia. In August 2025, PAHO highlighted the presence of two CHIKV genotypes circulating regionally the Asian and ECSA genotypes and their potential co-circulation, which could alter transmission dynamics in countries with high vector density such as Venezuela (66). The epidemiological risk in Venezuela is amplified by three converging factors: the high density of Aedes aegypti in urban and peri-urban areas of the coastal and plains states; low vaccination coverage, which has left pockets of susceptible individuals for multiple arboviruses; and the mobility of more than 7 million Venezuelan migrants who act as a two-way bridge for viral spread between Venezuela, Colombia, and Ecuador (70).

Following the 2014–2015 epidemic in Colombia, which recorded a total of more than 236,768 cases, with a national incidence rate of 396 cases per 100,000 inhabitants in 2014, the country experienced a sustained decline; in 2023, only 52 cases of CHIKV were reported, continuing the downward trend that began after the 2015 peak, which recorded approximately 276,000 cases (71). However, confirmed cases of CHIKV have been reported in the departments of Antioquia, Huila, and Santander in 2025, with an increase in frequency in 2026 compared to the same period in 2025 (72). This resurgence coincides with the continental alert issued by PAHO. In the first four months of 2023, an increase in CHIKV circulation was detected in the region, with more than 214,000 reported cases (73). A structural limitation in Colombia is the systemic underreporting of cases: studies estimated that 87% of cases were not reported to SIVIGILA, and in municipalities in the Colombian Caribbean such as Ovejas and Corozal, underreporting was estimated at 48.4% and 54.2%, respectively, implying that official figures represent only a fraction of the actual disease burden (74).

As for Zika, although incidence rates have remained low since 2017, the virus has been confirmed in 89 countries around the world; ten countries in the region account for 89% of the cases recorded between 2014 and 2023, with Brazil, Colombia, and Venezuela leading this list, with 27,000 cases reported in the Americas during 2023 (75).

In Ecuador, the last confirmed cases of Zika were reported in 2018, reflecting the relative effectiveness of national entomological surveillance and Aedes aegypti control during that period (76). In Colombia, 50 cases of locally transmitted Zika were confirmed since early 2024, making it the country with the second-highest number of cases in the Americas after Brazil during that same period (77). In Venezuela, the number of cases is not officially known; however, unofficial data indicate that since 2016, Zika cases have been systematically underreported (78). The WHO warned in September 2023 that most infections with this virus are asymptomatic or mild, which greatly hinders their detection by health systems, making Zika a silent epidemiological threat and posing a significant risk due to its teratogenic effects in non-immune pregnant populations (75).

In Latin America, the resurgence of infectious diseases is not limited to dengue; rather, it is part of a broader epidemiological pattern that is directly influenced by social, environmental, and migratory factors. Studies have documented that diseases such as dengue, chikungunya, and Zika have experienced sustained expansion in countries like Colombia, Venezuela, and Ecuador, highlighting that regional population mobility especially from Venezuela has contributed to the spread of arboviruses in neighboring countries, facilitating the introduction of new viral lineages and intensifying transmission. Likewise, these studies highlight that the reemergence of communicable diseases in the region stems from a complex interplay of ecological, socioeconomic, and political determinants, which shape a dynamic epidemiological landscape where multiple arboviral diseases and other emerging infections coexist. This context underscores the need for integrated approaches to epidemiological surveillance and control, particularly in Andean and tropical countries where the disease burden is rising (79–81).

The silent return of yellow fever

For several years now, yellow fever has posed an epidemic threat despite the availability of an effective vaccine, highlighting insufficient immunization coverage in areas considered endemic and the persistence of active jungle cycles (82).

Yellow fever had remained contained, limited to the Amazon basin and vaccination advisories for travelers; however, in the 2024 and 2026 periods, it surged, catching many health systems off guard.

In 2024, 61 cases were confirmed across the region, with 30 deaths a figure already higher than the 58 cases recorded from 2022 to 2023 in Bolivia, Brazil, Colombia, and Peru (83). What occurred exceeded all projections: in 2025, 346 confirmed cases and 143 deaths were reported in seven countries Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela representing an increase of more than 500% compared to the previous year (84, 85). During the first seven weeks of 2026, PAHO had already recorded 34 additional human cases and 15 new deaths, mainly in Bolivia, Colombia, Peru, and Venezuela (85).

In retrospect, in 2024, 61 human cases of yellow fever were confirmed in the Region of the Americas, of which 30 were fatal representing a case fatality rate of 50% spanning five countries: Bolivia, Brazil, Colombia, Guyana, and Peru; in response to this situation, however, PAHO/WHO declared an epidemiological alert for the region in January 2025 (86). Colombia declared a national health emergency: between 2024 and 2025, 43 cases were reported with a case fatality rate of nearly 50%, 74% of which were concentrated in the department of Tolima. It is noteworthy that the virus spread beyond its traditional endemic areas and infected densely populated areas with no recent history of the disease, such as the state of São Paulo (Brazil) and the department of Tolima (Colombia). PAHO facilitated the procurement of 1.3 million vaccine doses and achieved 50% coverage among the population aged 1 to 59 in prioritized municipalities (87, 88). As of May 2025, the regional situation had worsened considerably, with 221 confirmed human cases and 89 deaths reported in Bolivia, Brazil, Colombia (64 cases, 26 deaths), Ecuador (6 cases, 5 deaths), and Peru, with a more than eightfold increase in cases compared to the same period in 2024, leading PAHO to classify the risk as high in May 2025; nearly all cases occurred in unvaccinated individuals (89).

Colombia ended 2025 with a massive surge, recording 125 confirmed cases and 51 deaths (a case fatality rate of 36.8%), during which the virus broke from its traditional geographic pattern. A common finding identified by the Ministry of Health in its audits of fatal cases in Colombia is that many victims were men of working age (between 15 and 59 years old) engaged in agricultural work in forested areas, who had no history of yellow fever vaccination (90). For its part, Ecuador has maintained low sustained indigenous transmission; it had recorded its last indigenous case in 2017 and one imported case from Colombia in 2024; however, 11 cases were reported in 2025, with active surveillance maintained in the Amazonian provinces. The year 2025 ended with 346 cases distributed across 7 countries. Venezuela confirmed an active outbreak in 2026: between epidemiological weeks 1 and 7 of 2026, 6 confirmed cases were reported, including one death (case fatality rate: 17%), with 90 outbreaks in non-human primates documented during 2025 in the states of Apure, Aragua, Barinas, Carabobo, Guárico, Lara, Portuguesa, and Monagas (91),. The regional pattern shows a concerning spread of the virus out of the Amazon region toward periurban areas with high densities of Aedes aegypti, the vector for the urban form of the disease, which increases the risk of an epidemic of urban transmission in the three nations (Figure 1).

To date, strategies based on the global EYE strategy framework (2017–2026) constitute the priority actions for reducing the impact of yellow fever, with the primary objective of achieving a minimum routine immunization coverage of 95% in endemic areas and deploying urgent reactive vaccination campaigns to protect agricultural workers in forested areas (92, 93). It is important to note that, because the transmission cycle in the region is predominantly forest-based, control efforts require robust epizootic surveillance through the monitoring of mortality in non-human primates, which serves as an early warning system prior to the emergence of human cases (93).Furthermore, given the high case-fatality rates recorded in recent outbreaks, the Pan American Health Organization has standardized clinical management guidelines to optimize early hemodynamic support for severely ill patients (94), in addition to integrated vector management to suppress Aedes aegypti populations and thus rigorously eliminate the risk of the virus re-establishing itself in densely populated areas (93, 95).

West Nile virus in the Andean-Amazon corridor

There are other vector-borne viral diseases, such as West Nile fever, which has remained endemic in North America since its introduction in 1999, with sustained circulation in the United States and Canada, and reported cases in Mexico, in addition to evidence of the virus’s spread via migratory birds across the Americas, constituting diseases that also require attention, noting that many of these diseases are preventable through protective measures and active public participation, with an emphasis on the implementation of primary health care and vaccination campaigns where appropriate. In South America, the virus circulates enzootically; however, the true extent of its impact on public health is underestimated due to serious gaps in active surveillance. Circulation has been consistently documented in birds, equids, and mosquitoes; however, confirmed human cases remain disproportionately scarce compared to North America and Europe, with animal and vector evidence extending to Guatemala, El Salvador, Bolivia, Paraguay, Colombia, Venezuela, Cuba, and Ecuador. A significant finding in 2025 was the immunohistochemical and molecular confirmation of West Nile virus-associated poliomyelitis in a mule from southern Brazil, suggesting the possible entry of the virus into the central nervous system of equids as well as the spread of this virus to other geographic regions of this continental country (96, 97).

From January 2024 to December 2024, 110 cases were reported in 13 of Brazil’s 27 states; a retrospective study in the state of Ceará revealed that 12.1% corresponded to WNV cases, with a peak in 2023 when 42.6% of all cases occurred, 29 of which presented neurological complications and four resulted in death; phylogenetic analysis identified the circulation of lineage 1a (98). In the case of Colombia and Venezuela, available evidence suggests that the virus remains predominantly serological in equids; a study conducted on equids in 2004–2005 in the departments of Córdoba and Sucre (Colombia) identified specific antibodies against WNV in 9% of the animals, constituting the first evidence of transmission in South America (99). Meanwhile, in Venezuela, variable seroprevalence rates were documented in birds and equids in the central and eastern plains, constituting the first report of infection in South American birds and solid evidence of the virus’s establishment in a continuous transmission cycle on the continent (100). In Ecuador, seroprevalence studies conducted from 2009 to 2011 detected IgG and IgM antibodies against WNV in humans and equines in coastal areas and the Amazon basin, suggesting active viral activity (101). In 2026, a study concluded that human surveillance is predominantly passive and focused on neurological or encephalitic syndromes, with variable animal and vector surveillance ranging from limited to focal in most Latin America countries (96), suggesting that the actual burden of WNV in the Andean-Amazonian subregion is likely much higher than reported.

Immunization outlook: immediate action against the invisible threats of the future

The landscape of vaccination against emerging arboviral diseases in Latin America reveals a gap between the speed at which pathogens spread and the pace of development of preventive tools and increases in vaccination rates as is the case with yellow fever, particularly among vulnerable populations. In recent years, the region has been considered critical in the global epidemic landscape due to the exponential increase in arboviral diseases, including yellow fever, chikungunya, Zika, dengue, and, more recently, Oropouche fever, a combination that poses increasingly complex epidemiological challenges (102).

The landscape of vaccination against emerging arboviral diseases in Latin America reveals a gap between the speed at which pathogens spread and the pace of development of preventive tools and increases in vaccination rates as is the case with yellow fever, particularly among vulnerable populations. In recent years, the region has been considered critical in the global epidemic landscape due to the exponential increase in arboviral diseases, including yellow fever, chikungunya, Zika, dengue, and, more recently, Oropouche fever a combination that poses increasingly complex epidemiological challenges (102). At the same time, the first computational design of a multi-epitope vaccine against OROV targeting the envelope polyprotein was reported, using bioinformatics, molecular modeling, and immune simulation; however, no candidate has yet reached the clinical phase (103).

In the case of chikungunya, the situation is mixed: although Ixchiq (Valneva, France) was the first vaccine against an alphavirus to be approved by the FDA in November 2023, its license in the United States was suspended in August 2025 due to safety concerns; however, VIMKUNYA (Bavarian Nordic, Denmark) received approval as an alternative, and multiple candidates for other arboviral diseases in the same family are at various stages of the development pipeline, opening up new vaccination technologies applicable to related viruses that could cause future epidemics (104).

As for Zika, Phase 2 trials of Moderna’s mRNA-1893 candidate and the NIH’s DNA vaccine are still ongoing, with neither having reached Phase 3. Against this backdrop, recent and ongoing outbreaks of Oropouche and yellow fever highlight significant gaps in surveillance, diagnosis, clinical management, and prevention situations that must be urgently addressed to strengthen preparedness and response, while the WHO has launched the Global Initiative against Arboviruses as a framework for coordinated action to address this multiviral threat (105).

Determinants of the re-emergence of diseases in the Andean-Amazonian corridor and addressing them through the One Health approach

The integration of the One Health approach, genomic surveillance, and proactive prevention strategies provides a strategic framework for combating emerging infectious diseases in the region, which is characterized by critical risk factors such as rapid deforestation that erodes ecological barriers between wildlife and human communities, fragmented health systems unable to respond to outbreaks in real time, and a wealth of biological diversity that harbors an inexhaustible reservoir of pathogens with zoonotic potential. It is important to bear in mind that human, animal and environmental health form a single continuum and that, when this is overlooked, certain arboviruses such as dengue, Zika and Chikungunya spread unchecked.

Common determining factors have been identified that highlight the vulnerability of the three countries to outbreaks of emerging diseases; these factors constitute risk links at the human-animal-environment interface (106).

Climate change has had numerous effects worldwide; the recent surge in disease outbreaks is attributed to certain factors, such as rising temperatures, extreme rainfall, and the geographic spread of the Aedes aegypti mosquito (106).

In summary, as documented in 2024, dengue, Chagas disease, leishmaniasis, and malaria were the re-emerging diseases with the strongest documented association with climate variations. The WHO’s Global Report on Arbovirus Preparedness (2025) notes that dengue recorded more than 14 million cases annually in 2024, constituting the highest figure recorded to date and evidencing a substantial increase in the global burden of the disease in recent years (107–109). Given these crucial aspects, an interdisciplinary approach is necessary.

In addition to inadequate health education in certain sectors, deficiencies in vector control programs, and cross-border population mobility between Colombia, Ecuador, and Venezuela—exacerbated by the Venezuelan migration crisis (110). These factors facilitate the rapid spread of pathogens. Given this situation, there is an urgent need to implement critical control points for an immediate response to outbreaks, based on the framework of the International Health Regulations (IHR 2005), the One Health approach, and current PAHO/WHO recommendations established for the region (111, 112).

In September 2021, the Directing Council of the Pan American Health Organization (PAHO) approved the One Health policy as an approach to address health threats at the human-animal-environment interface (CD59/9), seeking not only a comprehensive but also an inclusive approach so that the Organization can work with its Member States, particularly in the region of the Americas, which is considered highly exposed to the risk of the emergence and re-emergence of zoonotic pathogens with a high risk of transmission to human populations. To this end, the implementation of systematic, coordinated, collaborative, multidisciplinary, and intersectoral policies is sought, which is highly appropriate for addressing zoonotic diseases and emerging and re-emerging infectious diseases (EIDs) (113).

It is important to note that the One Health approach has been implemented primarily in underserved rural and urban areas where socioeconomic conditions are poor, particularly in countries such as Brazil, Chile, and Colombia; however, the shortage of healthcare professionals and limited medical resources necessitate that professionals work as a team. Initially, links were established with indigenous communities, and work was carried out through community partners as tools for disease prevention and control. These efforts preceded this new approach aimed at building a healthier world characterized by inclusion, equity, and equality, where collaborative, multidisciplinary, political, and economic initiatives with a prosocial focus can become investments to address global, economic, and health challenges (114).

In the event of an outbreak, genome sequencing is a useful tool for tracing the source, predicting transmission routes, and guiding targeted public health interventions. This is why, in recent years, genomics has been considered the cornerstone of outbreak investigation, surpassing traditional diagnostic tools in detecting new pathogen strains, determining their genetic composition, and predicting antimicrobial resistance (AMR) (115, 116). Through these analyses, which integrate sequencing data with contextual metadata to reconstruct detailed transmission networks and outbreak dynamics, it is possible to identify sources of infection, trace transmission routes, and design more effective control strategies, marking a departure from the conventional approach based solely on case data (117–119). However, Latin America faces severe structural gaps. Low sequencing rates in several countries across the region underscore the urgent need to strengthen public health infrastructure and improve access to genomic diagnostic technologies.

The urgency of adopting a One Health approach in Latin America should not be justified solely by the burden posed by reported cases, but above all by the magnitude of what remains undetected or unreported. While clinical data are very valuable, they are insufficient if not accompanied by deep and sustained awareness across all relevant sectors: human health, animal health, the environment, agriculture, urban planning, and communities. Knowledge distributed at the community level rather than centralized solely in reference laboratories constitutes a fundamental line of defense.

Before the One Health community training programs, many communities lacked structured systems for real-time disease surveillance, awareness of zoonotic diseases, and environmental hygiene. Once trained, communities changed their practices, and volunteers reported symptoms more quickly, enabling a coordinated response to new cases (120, 121).

To truly achieve cross-sectoral awareness, sustained investment in education and training is needed to build a workforce capable of operating at the intersections of human, animal, and environmental health. Collaboration among physicians, veterinarians, ecologists, biologists, and policymakers is essential and must be facilitated through platforms that enable information exchange among the public health, animal health, and environmental sectors. Additionally, national and international risk assessment capacities must be strengthened to simultaneously address all facets of health (Figure 2).

It is also necessary to act on two fronts simultaneously: mapping and improving national and regional surveillance capabilities at the human-animal-environment interface; establishing mechanisms for real-time data exchange and integrated analysis; and strengthening laboratory networks and genomic surveillance capabilities. All of this must be integrated into a genuine commitment to cross-sectoral awareness-raising that transforms passive actors into active agents of epidemiological preparedness. Without sustained investment in these One Health-based capacities, with genuine community participation, the region will continue to react to epidemics rather than anticipate them, paying the highest price in life, the economy, and public health sovereignty.

Ecuador, Colombia, and Venezuela form a highly complex epidemiological corridor in which the threats posed by emerging diseases are simultaneous, evolving, and increasingly interconnected. Analysis of data recorded in recent years reveals that the epidemiological vulnerability of these countries is the cumulative result of political decisions, insufficient investment in public health systems, vaccination coverage below herd immunity thresholds. In addition to the fact that Venezuela suspended the publication of its epidemiological bulletins in November 2014 and, in 2018, abolished the Venezuelan Center for Disease Classification the agency responsible for reporting morbidity and mortality indicators to PAHO and WHO which created a gap in epidemiological data lasting several years.

Yellow fever has shown that it can have a case fatality rate of 59% among those infected in Venezuela and 45.3% in Colombia when detection is delayed, vaccination coverage is insufficient, and the response arrives months late. Dengue has shown that it can triple its cases in a single year when vector control systems weaken and cohorts of the population without immunity accumulate, or when other major health events occur, such as the COVID-19 pandemic, which had a high impact on health systems, focusing attention on this event as required, but which drastically affected the control of other diseases. Oropouche has demonstrated that it can spread beyond the Amazon basin without regional surveillance systems being prepared to detect it. These are not exceptions.