Origins of monkeypox viruses and their strains circulating in 2022

Abstract

Monkeypox has spread unprecedentedly to nearly 100 countries and infected more than 51,000 people since 1 May 2022. This large-scale outbreak constituted a public health emergency of international concern (PHEIC), as declared by the World Health Organization. To better recognize and control this outbreak, we explore here through phylogenetic analysis the origins of MPXVs and their strains circulating in 2022, which remain unclear so far. Our results suggest that MPXVs possibly originated from some cowpox viruses and three lineages of MPXVs within Clade IIb circulated in 2022. Our results also suggest that two MPXVs respectively similar to the two MPXVs exported from Nigeria to the USA in 2021, ON676708/USA/2021 and ON676707/USA/2021, evolved into two lineages and sparked the large-scale outbreak in 2022, after their unknown evolutionary and epidemiological journeys possibly in Nigeria, the USA, or other countries before May 2022. This view does not stigmatize any country, because monkeypox is an endemic zoonosis in west Africa with wildlife reservoirs, and its large-scale outbreak in 2022 also resulted from the global decline of population immunity against smallpox due to the cease of vaccination against smallpox decades ago.