Mutations in the virus causing the monkeypox epidemic?

Mutations in the virus causing the monkeypox epidemic?

Thousands of confirmed cases of monkey pox in the world, new contaminations identified every day, and a virus which arouses more and more fears on the globe. Thursday, the world health organization (WHO) has called on countries to be vigilant and transparent in the face of this outbreak of an unusual scale, and has brought together international experts to determine whether the situation constitutes a “public health emergency of international concern”, as it is the case for the pandemic Covid-19.

An unusual upsurge

Since the beginning of May, an unusual upsurge has been observed outside the countries of Central and West Africa, where the virus is endemic while usually generating relatively few cases there. Since the three cases of monkeypox identified a little over six weeks ago in the United Kingdom, none of which had recently traveled outside the country, the contaminations have been increasing.

“More than 3,200 confirmed cases of monkeypox and one death have been reported to WHO in 48 countries, including Nigeria,” WHO Director General Tedros Adhanom Ghebreyesus said. In France330 cases have been identified, according to the latest figures from Public Health France.

“In addition, since the beginning of the year, nearly 1,500 suspected cases (…) and around 70 deaths have been reported in Central Africa, mainly in the Democratic Republic of Congo, but also in the Central African Republic and Cameroon”, continued the head of the WHO. “We did not expect to have such a large number of cases. And it is a bit difficult to see what is the tip of the iceberg”, in particular because screening is not easy, said Philippe Duneton, executive director of Unitaid, an organization which helps poor countries to prevent, diagnose and treat diseases.

47 mutations identified in the current strain

In the current outbreak, of which Europe is to this day the global epicenter, the majority of cases so far have been among men who have sex with men (MSM). Although transmission can occur through close contact, such as sexual intercourse, smallpox is not a sexually transmitted infection.

How can this epidemic emerging from its endemic cradle be explained? That’s the answer they’re trying to find researchers from the Institute of Evolutionary Biology from the University of Edinburgh in Scotland, who analyzed the monkeypox genome and found an abnormally high number of mutations. Unlike Covid-19, which is an RNA virus and is capable of carrying dozens of mutations, monkey pox is an enveloped double-stranded DNA virus of the Poxviridae family. And in this family, to which classic smallpox belongs, the mutation rate of the virus is rather one to two mutations per year. However, by comparing the current strain of monkeypox to the strains that caused infections between 2017 and 2019, the researchers discovered no less than 47 mutations in the new version.

Among them, 42 bear the distinct signature of an antiviral enzyme called “Apobec3”, which is supposed to help the immune system force the virus to make mistakes when it replicates, and thus cause it to self-destruct. While monkeypox was originally “considered a zoonotic virus with limited human-to-human transmission, this long branch [de mutations] may be proof of an adaptation of the virus to humans,” say the researchers. And from now on, it is to contaminated humans that it is recommended to avoid pets so that they do not transmit the virus to them.

“Sustained human-to-human transmission” for several years

Known in humans since 1970, monkey pox, or “simian orthopoxvirus”, is nevertheless a disease considered rare, caused by a virus transmitted to humans by infected animals. Thus, many cases in Africa were attributed to contact with wild animals. However, in the current outbreak, human-to-human transmission is at the forefront. So much so that the WHO considers it likely that the actual number of cases is higher, and considers that the virus must have already been circulating before the current outbreak – possibly since 2017 – without its transmission being detected.

A hypothesis that is supported by the analysis carried out by the Scottish researchers, who believe that “the pattern we see in these monkeypox genomes since 2017 indicates replication in humans, and that the inheritance of specific changes that have occurred between 2017 and 2018, then in viruses from 2022, means there has been sustained human-to-human transmission, since at least 2017.”

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