A retrospective genomic characterisation of the 2022 mpox outbreak in Belgium, and in vitro assessment of three antiviral compounds.

BACKGROUND

Since the beginning of May 2022, cases of mpox have been reported in several European and American countries where the disease is nonendemic. We performed a retrospective genomic characterisation of the 2022 mpox outbreak in Belgium, and assessed the in vitro sensitivity of three antiviral compounds to a monkeypox virus (MPXV) strain from the 2022 outbreak.

METHODS

We sequenced the complete genomes of MPXV isolated from skin-, throat-, anorectal- and genital swab samples using the Oxford Nanopore Technologies (ONT) GridION. We subsequently analysed high-quality complete MPXV genomes and conducted a genomic analysis of MPXV complete genomes from this study with all other complete MPXV genomes available on GISAID up to October 28th, 2022. The in vitro activity of tecovirimat, brincidofovir, and cidofovir was also tested in human and monkey cell lines.

FINDINGS: We produced 248 complete MPXV genomes. Phylogenetic analysis of the complete MPXV genomes revealed that they all belong to MPXV Clade IIb B.1. Surprisingly, through phylogeographic analysis we identified a minimum number of 79 introduction events into Belgium, along with sustained local transmission. We also demonstrated the superior in vitro efficacy and selectivity of tecovirimat to the 2022 MPXV clinical strain.

INTERPRETATION: The number of sequences provides sufficient information about the MPXV lineages that were circulating in Belgium. The 2022 mpox outbreak, in Belgium, was mainly characterised by many introduction events that were promptly contained and resulted in limited human-to-human transmission of MPXV. The in vitro efficacy of antivirals against a 2022 MPXV Belgian strain highlights the potent activity and specificity of tecovirimat and its ability to prevent the formation of the extracellular enveloped viruses.

FUNDING: None.