Detection of dengue, malaria, and additional causes of acute febrile illness: The need for expanded testing, Bayelsa State, Nigeria

Dengue virus (DENV) infection has not been previously reported from Bayelsa State, Nigeria. We aimed to determine the prevalence of dengue virus (DENV) infection, malaria, and coinfection, and other pathogens among febrile patients in the capital city, Yenagoa.We conducted a cross-sectional study among persons aged ≥1 year who presented with acute febrile illnesses (AFI) at four hospitals in Bayelsa State during 20 May - 15 June 2022. Blood samples from 443 participants were tested for DENV seromarkers (NS1, IgM, IgG), using serology and RT-PCR, and malaria was diagnosed by thick smear microscopy. Sociodemographic and risk factor data were collected using electronic questionnaires administered via smart phones/tablets and analyzed using univariate and multivariate methods. Metagenomic libraries were prepared and enriched by viral target capture and sequenced by NGS. The seroprevalence of acute DENV infection was 14.5% (n = 64) while the prevalence of malaria was 42.4% (n = 188); 6.5% (n = 29) of participants were coinfected with acute DENV infection and malaria. An additional 17.6% (n = 78) of participants had markers for past DENV infection. Rural/suburban residence and age ≥ 31 years were significantly correlated with having any dengue seromarker. Residence in a larger household (≥5 persons), and borehole water-use were predictors for malaria fever. RT-PCR results revealed multiple DENV serotypes, with serotype 3 dominant. Sequencing of unknown AFI cases revealed numerous viral causes such as adenovirus, EBV, and hepatitis A, as well as additional dengue and malarial infections missed by conventional testing. Of interest were Coxsackievirus A5 (hand, foot and mouth disease; HFMD) which has been diversifying locally for years in Nigeria and an mPox clade IIb (lineage A.2.3) strain that emerged in Nigeria during the 2022 global outbreak. The results of this study provide the first documentation of human DENV infection in Bayelsa State, Nigeria and suggests that dengue is an emerging and important cause of febrile illness in this area. Our findings support the need for routine testing to identify DENV among patients who present with acute febrile disease. Metagenomic NGS results highlight the benefits of unbiased surveillance to identify circulating and emerging pathogens.