Colourised transmission electron micrograph of mpox virus particles (red) found within an infected cell (blue), cultured in the laboratory.Credit: NIAID
Human-to-human transmission, rather than zoonotic spillover, is the driving force behind a surge in Mpox virus cases, according to a study in Science.
The Mpox virus (MPXV) has diversified into several distinct lineages in the human population, marked by significantly faster heightened mutation rates.
The research team, from Nigeria, the United States, South Africa, and Europe, reported that the sequencing of the initial human cases of the virus, which were identified in regions beyond countries with established historical reservoirs in 2022, revealed that the cases exhibited “42 nucleotide differences from the nearest known MPXV, previously sampled”.According to the study, MPXV genome sequences from the 2022 epidemic show a higher rate of mutation than would be expected for double-stranded DNA viruses when compared to sequences from 2018.
Áine O’Toole, from the University of Edinburgh’s Institute of Ecology and Evolution, and colleagues who developed a molecular clock method to evaluate the evolution of MPXV says the mutations are characteristic of the action of human enzyme, APOBEC3.
“MPXV genome sequences show more mutations than would be expected of a poxvirus over such a short period of time. Our analysis shows that APOBEC3 has been generating these mutations as part of an antiviral mechanism, raising questions of longer-term viral fitness,” said O’Toole.
O’Toole says estimates show that these mutations began accumulating at least as early as 2016, suggesting MPXV has been transmitting in the human population since then, a big change from its previous classification as a primarily zoonotic virus.
