Mpox was circulating for some years before 2022 breakout, study finds

The spread of mpox in 2022 led to various vaccination campaigns, including in Switzerland. Copyright 2022 The Associated Press. All Rights Reserved

Mpox (formerly known as Monkeypox) has been circulating among humans since 2016. This discovery represents a paradigm shift, a research team with Swiss participation wrote in the “Science” journal on Thursday.

“The origin of the surprising epidemic of 2022 therefore dates back some time,” study co-author Richard Neher from the University of Basel told the Keystone-ATS news agency.

Until recently, mpox was considered a zoonotic disease, that is, transmitted by animals. After the first cases in humans were discovered in the 1970s, most subsequent episodes have been considered isolated transmissions, with only a few affected people in the human population.

But the situation changed in 2022: the fact that mpox suddenly appeared outside countries where infected animals were known indicated that the spread of the virus was no longer just a zoonotic infection.

More mutations than expected

The research team analysedExternal link the genetic sequences of the 2018 and 2022 monkeypox viruses and found that the DNA sequences differed more than expected.

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According to the study, most of these mutations are modifications of constituent elements of the genetic heritage due to the activity of a defense enzyme of the human immune system called APOBEC3.

The researchers see this as a sign that mpox is spreading through the human population instead of passing sporadically from animals to humans. Based on the rate of mutations per year, they estimated that the latest strain has been circulating in the human population since at least 2016.

“But there is no indication that these mutations have modified the virus significantly,” particularly with regard to its transmissibility, Neher said.

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