The monkeypox strain behind the recent outbreak in Europe and North America has mutated far more than expected, according to an article published in Nature Medicine by Portugal's National Institute of Health Dr. Ricardo Jorge (INSA) on Friday.
A surprising number of mutations
The strain in the current outbreak has been linked to the West African clade, which has a less than 1% fatality rate. The researchers found that the strain currently circulating diverges from the related earlier strains by an average of 50 mutations, about six to 12 more than one would expect considering previous estimates of the mutation rate for this type of virus.
Some of the mutations in the monkeypox strain circulating could have increased the infectivity of the virus as well, according to the researchers.
"[M]ultiple mutations that we are seeing during the 2022 person-to-person transmission affect proteins associated with the human immune system, so it might mean a process of adaptation to humans," said João Paulo Gomes, PhD, of the INSA to MedPage Today. "And, yes, it seems to occur in a faster rate than expected, which is in line with the also unexpected observation of the excess of mutations of the 2022 [strain] when compared with its ancestor."
The researchers stated that it is likely that the recent outbreak was recently imported from a country where the virus is endemic, although it could have been that it was spreading silently for a prolonged period in humans or animals in non-endemic countries before it was recently detected.
Another possible situation is that the outbreak began from more than one origin, with a superspreader event or events triggering a rapid spread.
Since the beginning of May, over 3,000 cases of monkeypox in 47 countries have been reported to the World Health Organization (WHO), including in many countries where the virus had not previously been reported.