Beyond the epidemic curve: a critical systematic review of the structural, ecological, and viral determinants sustaining Chikungunya and Zika viruses in Latin America and the Caribbean.

Background: The incursion of Chikungunya (CHIKV) and Zika (ZIKV) viruses into Latin America and the Caribbean (LAC) after 2013 created complex epidemics with high attack rates, severe complications, and persistent transmission. While individual aspects have been studied, a synthesized understanding of the interacting viral, ecological, and social drivers sustaining these arboviruses in the region remains lacking. Objectives: To critically synthesize evidence on the incursion and establishment of CHIKV and ZIKV in LAC through an integrative framework examining the interaction between viral adaptation and structural vulnerabilities. Design: Systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. Data sources and methods: We systematically searched PubMed, EMBASE, Scopus, and LILACS, supplemented by gray literature from PAHO, WHO, and CDC, for studies published between January 2013 and December 2025. Eligible studies included observational studies, surveillance data analyses, outbreak reports, modeling studies, and genomic epidemiology focusing on CHIKV/ZIKV incursion, transmission dynamics, establishment, burden, or socio-ecological determinants in LAC populations. Two independent reviewers performed screening, data extraction, and quality assessment using Joanna Briggs Institute tools. A critical narrative synthesis was conducted using the novel Results: Eighteen studies met inclusion criteria. Pathogen plasticity-evidenced by multiple independent introductions, genetic variability, and cryptic transmission (e.g., an unreported 2017 ZIKV outbreak in Cuba uncovered through travel-genomic surveillance)-exploited profound structural vulnerabilities. These included weak surveillance systems (detection rates as low as 1%-6% for ZIKV), inadequate water and sanitation infrastructure driving a knowledge-practice gap (75.2% knowledge vs 30.7% adequate practices), and socioeconomic inequities that concentrated disease burden. Severe impacts were disproportionately borne by marginalized groups, quantified by a 9.0-year disparity in average Years of Life Lost between Black (22.0 years) and White (13.0 years) Brazilians with Chikungunya. Despite the epidemic's waning, 58% of analyzed locations remain at high risk for future ZIKV outbreaks due to discrepancies between environmental suitability and population immunity. A critical geographical evidence bias was identified: 13 studies (72%) were conducted in Latin America (primarily Brazil and Colombia), while only 5 (28%) focused on the Caribbean region, limiting generalizability to smaller island states. Conclusion: The establishment of CHIKV and ZIKV in LAC represents a biosocial process wherein adaptable pathogens exploit and reinforce structural inequities. Achieving durable resilience requires integrated surveillance platforms that monitor both pathogens and social vulnerabilities, coupled with fundamental investment in water, sanitation, waste management, and equitable healthcare infrastructure to interrupt the vicious cycle of arboviral emergence. Trial registration: PROSPERO CRD420251242134 (available at: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251242134).