First laboratory-confirmed fatal dengue virus infection and its implications for national arboviral surveillance in Liberia.

Introduction: Dengue virus (DENV) is an emerging public health threat in Africa, where its impact is underestimated due to nonspecific clinical manifestations and restricted diagnostic capabilities. In Liberia, laboratory-confirmed cases of DENV were initially recorded in an urban febrile surveillance study (2018-2020), yet severe or fatal outcomes had not been previously reported. This paper reports the first laboratory-confirmed fatal dengue case and its implications for national surveillance and policy in Liberia. Case report: On February 2, 2026, a 38-year-old Liberian man arrived at J. J. Dossen Memorial Hospital in Maryland County, located in the southern region of Liberia, with a 2-day history of high fever, severe headache, myalgia, weakness, and abdominal discomfort. He had no recent history of travel. The first laboratory investigation using a rapid test and microscopy ruled out malaria. Molecular detection performed at the National Public Health Reference Laboratory was negative for Lassa, Ebola, and Marburg. Despite management with supportive care, his condition deteriorated clinically upon readmission, and the patient died on February 6, 2026. Serological testing performed at MDS-Lancet Laboratories, Ghana detected DENV immunoglobulin G antibodies and yielded a positive nonstructural protein 1 antigen result, prompting further investigations. Consequently, a blood sample was referred to the Institut Pasteur de Dakar, Senegal, where confirmatory testing was conducted to include differential reverse transcription polymerase chain reaction for a diverse array of arboviruses and viral hemorrhagic fevers and differential virus-specific immunoglobulin M (IgM) enzyme-linked immunosorbent assay. The sample tested positive for DENV ribonucleic acid by reverse transcription polymerase chain reaction, negative for other viruses, and negative for dengue-specific IgM. The absence of detectable IgM may reflect specimen collection during an early stage of infection before seroconversion. However, IgM negativity alone cannot distinguish between primary and secondary infection. Conclusion: This is the first molecular confirmation of fatal dengue in Liberia. It highlights the potential for severe outcomes and suggests locally acquired transmission in southeastern Liberia, a region bordering Côte d'Ivoire. There is a critical need for swift implementation of integrated arboviral surveillance in both urban and rural settings, better diagnostic capabilities, and possibly a nationwide seroepidemiological study to estimate the actual burden of dengue in the country.