Severe dengue outbreak associated with DENV-3 in the city of Manado, North Sulawesi, Indonesia.

Abstract Background During early 2019, outbreak of dengue with severe manifestation was reported in Manado, North Sulawesi province, Indonesia. This epidemic has raised public concern and recorded the highest number of cases in the last ten years. This study aims to determine the clinical spectrum, disease etiology, and virological characteristics associated with the epidemic of severe dengue. Methods Dengue was diagnosed using NS1 detection, RT-PCR, and IgG/IgM serology. Envelope gene sequencing was conducted to determine the phylogeny of the dengue virus (DENV). Results We recruited 146 patients with a median age of eight years (IQR = 5 – 11 years). Most patients experienced expanded dengue syndrome, characterized by severe organ involvement including liver enlargement, stomachache, and coagulation problems. During the outbreak, DENV-3 was the dominant serotype (75.9%). Smaller numbers of DENV-1, -2, and -4 were also detected. Phylogenetically, the dominant DENV-3 strains grouped into multiple clusters and were related to other Indonesia strains, suggesting the emergence of heterogenous local viruses. Conclusion We confirmed the occurrence of a severe dengue outbreak in Manado and detected DENV-3 as the dominant serotype during the outbreak. Our study demonstrates the benefits of virological surveillance in understanding the etiological agents responsible for outbreak of severe dengue.