Emerging viruses are an underestimated cause of undiagnosed febrile illness in Uganda

SUMMARY Background Viruses that cause acute febrile illness (AFI) in sub-Saharan Africa cause a spectrum of disease from mild to life-threatening. Viral infection is often undiagnosed, as routine diagnostics are insufficient to capture the diversity of circulating pathogens. Methods 1281 patients with fever of 2-7 days were prospectively recruited from three sites in Uganda as part of the CDC-UVRI AFI Study and screened with enhanced diagnostics. Plasma from 233 undiagnosed patients was analysed using metagenomic next-generation sequencing (mNGS). Confirmatory testing was carried out by PCR and serology. Findings Thirty-eight viral pathogens were identified by mNGS in 35/233 (15%) undiagnosed patients including Measles, Hepatitis A/B/E viruses, Human immunodeficiency virus-1, Rhinovirus, Rotavirus-like virus, Human herpesvirus 6B, Human parainfluenza virus 3 and Enteroviruses. Four high-consequence arboviruses were found in six patients; Crimean-Congo haemorrhagic fever virus, Rift Valley fever virus, dengue virus and yellow fever virus. Le Dantec virus, last reported in 1969, was detected and confirmed by serology in one patient (and a contact of that patient). The majority of patients (23/30; 76%) diagnosed with an acute viral infection were treated with antibiotics and/or (12/30; 40%) antimalarials. Interpretation AFI in Uganda is commonly associated with undiagnosed viral infection, including high-consequence and rarely reported viruses. This highlights an ongoing risk to public health and the need for improved vigilance. MNGS alongside diagnostic serology is a powerful method for clinical surveillance to investigate circulating viral pathogens. Cost-effective diagnostic assays should be adapted according to regional needs for testing.