New research may change the narrative about how mpox, formerly known as monkeypox, has become a human problem. Researchers found evidence that strains of the virus have been circulating among humans since at least 2016, years before it caused a surprise global epidemic in 2022. Although reported cases of the viral disease have slowed considerably since then, the findings suggest that It will be even slower. More difficult than expected to completely eradicate the disease.
First we realized monkeypox in the 1950s, when it caused an isolated outbreak among laboratory monkeys that had been transported from Africa to Denmark. In the 1970s, the first known human cases were documented. The monkeypox virus is a close relative of smallpox and, like the extinct virus, the infection tends to cause skin rashes and flu-like illnesses in its victims.
Monkeypox, now officially called mox, has long been considered a zoonotic disease, transmitted primarily from animals (probably rodents, not monkeys) to humans and rarely transmitted between people. But that perception changed in early 2022, when the virus began causing widespread human-to-human outbreaks outside of Africa.
These shoots covered worldwide, with more than 90,000 cases in 115 countries documented as of January 2022. The virus can spread through any type of direct contact, but these cases have largely been sexually transmitted between gay and bisexual men. Fortunately, the strains that spread widely belonged to less lethal clades of the virus, although at least 157 deaths have been attributed to the epidemic.
It is still unclear exactly how mpox managed to break free from its known confines and spread around the world. But a team of researchers from the University of Edinburgh and elsewhere say they have been able to uncover one of the important aspects behind its emergence: its recent evolutionary journey before 2022.
Like previous studies, researchers found that the first epidemic strains of monkeypox in 2022 belong to the same lineage of strains documented in 2018 that originated in Nigeria, one of the areas in Africa where zoonotic transmission of the disease is endemic. . But these latest strains have many genetic differences compared to the 2018 version. One possible explanation for this divergence is that, between those years, one or more of these strains mutated rapidly within humans, and these mutations allowed the virus to spread. adapt and spread more easily among people from then on.
However, according to the study’s authors, this scenario doesn’t make much sense, based on what we know about the rate of evolution of other similar viruses. The team identified that almost all of these mutations affected how the virus would respond to an antiviral enzyme our cells produce called APOBEC3. They argue that these changes are actually a result of the virus gradually adapting to us, suggesting that sustained human transmission of mpox has been occurring for much longer than we thought. Using these APOBEC3-related mutations as a window to the past, researchers now estimate that some strains of mpox have been spreading among humans since at least 2016.
“These observations of sustained MPXV transmission present a fundamental shift in the perceived paradigm of MPXV epidemiology as a zoonosis,” the team wrote in their paper. published Thursday in Science.
The findings, assuming they are validated by other research, should not only change the way we think about mpox’s past but also its future, the authors say. Other lineages of the virus still exist, so they may also be spreading or may one day spread among humans. And although the current epidemic has subsided substantially (thanks in part to vaccination and awareness campaigns in high-risk communities), it is has not gone.
To truly get rid of mpox will require much more vigilance than is currently practiced, the authors say.
“It is critical that global public health give MPXV cases in countries historically considered to have endemic reservoir species the same attention and concern as those elsewhere,” they wrote. “Surveillance must be global if MPXV is to be eliminated from the human population and then prevented from re-emerging.”