Serological and Immunological Markers in Dengue Fever: A Retrospective ELISA-Based Pilot Study from Trinidad and Tobago

Dengue fever remains a major mosquito-borne viral disease in tropical and subtropical regions and continues to represent an important public health challenge in the Caribbean. Despite endemic transmission in Trinidad and Tobago, limited laboratory-based studies have evaluated serological markers associated with recent dengue infection. A retrospective laboratory-based pilot study was performed using anonymized serum samples collected between September 2025 and February 2026. Anti-dengue virus IgM antibodies were detected using a commercial enzyme-linked immunosorbent assay (ELISA). Results were classified as positive, borderline or negative according to manufacturer-recommended criteria. Descriptive statistical analysis was performed to determine seroprevalence and distribution of serological reactivity. A total of 161 serum samples were analysed. Twenty samples (12.4%) demonstrated positive anti-dengue IgM reactivity, while 29 samples (18.0%) showed borderline reactivity and 112 samples (69.6%) were negative. The findings suggest ongoing dengue virus circulation within the study population. Borderline results may reflect early seroconversion, declining antibody titres, secondary dengue infection or flavivirus cross-reactivity. Epidemiological analysis demonstrated concordance with known seasonal dengue transmission patterns in Trinidad and Tobago. This pilot study provides preliminary evidence of recent dengue virus exposure within Trinidad and Tobago and highlights the usefulness of ELISA-based surveillance in endemic settings. Although limited by retrospective design and absence of molecular confirmation, the findings support continued laboratory surveillance and future prospective studies incorporating RT-PCR, NS1 antigen testing and paired serological analysis.