Whole-genome sequencing and phylogenetic analysis of the first and second confirmed cases of human infection with Monkeypox virus from Sierra Leone

Abstract

Whole-genome sequencing and phylogenetic analysis of the first and second confirmed cases of human infection with Monkeypox virus from Sierra LeoneTo the Editor, We read with great interest the letter by Yadav and colleagues, which detailed the need to focus on understanding the evolutionary trajectory of monkeypox virus. 1 The monkeypox virus (MPXV) is genetically classified into four primary clades (Ia, Ib, IIa, IIb).Notably, the newly identified clade Ib has emerged as the dominant strain in the current Public Health Emergency of International Concern (PHEIC), exemplified by the ongoing outbreak in the Democratic Republic of the Congo. 2 Concurrently, global transmission of clade IIb MPXV persists, underscoring that the ongoing epidemic warrants serious attention.On January 10-11, 2025, Sierra Leone released the case reports of its first two human infections with monkeypox virus during the PHEIC, becoming the final member of the Mano River Alliance to document such cases.Here, we present the two case studies with viral sequencing insights, shedding light on MPXV evolution in West Africa.Case 1 was a male in his twenties working as a car dealer who presented to the hospital in early January.He had traveled to Lungi (Port Loko District) from 26 December 2024 to 5 January 2025 (Fig. 1A).Symptom onset occurred on 6 January.Case 2, a male staff at a restaurant over 20 years old, developed symptoms on 6 January and sought hospital care in January.Both of the vesicle samples were confirmed MPXV-positive by real-time PCR using Monkeypox Virus Nucleic Acid Detection Kit at the Molecular Laboratory of 34th Military Hospital in Sierra Leone on January 10 and 11, respectively (Fig. 1A; Fig. S1 in the Appendix).Mean cycle threshold values were 20.29 for Case 1 and 15.14 for Case 2. The patients were admitted to the infectious disease isolation unit and were managed appropriately.Pre-rash symptoms included fever and headache, with rash involvement of the face, palms, and other cutaneous sites (Fig. S2 in the Appendix).Case 2 additionally presented with genital rashes with dysuria.Both patients denied animal/known case exposure, blood transfusions, travel (except for Case 1's documented trip, Journal of Infection 91 (2025) 106587