About 5,000 cases of monkeypox in humans have been reported worldwide this year. The researchers say the mutation rate of the virus is “surprisingly high”.
According to the study, the causative agent of the current monkeypox epidemic has mutated surprisingly strongly. Compared to related viruses from 2018 and 2019, there are about 50 differences in the genome, the team from Portugal writes in the journal Nature Medicine.
This is far more than would be expected based on previous estimates for this type of pathogen: approximately 6 to 12 times more. A divergent branch could be a sign of accelerated evolution. The work is mainly based on analyzes of Portuguese cases.
Until now, experts have talked about the generally rather slow development of this type of virus – especially compared to the very numerous mutations of Sars-CoV-2.
The authors of the study suspect one or more imports from a country where the virus is permanently present behind the current epidemic. Superspreading events and international travel then seemed to promote further spread. “Our data provide further evidence of ongoing viral evolution and possible adaptation to humans,” writes the team led by João Paulo Gomes of the Doutor Ricardo Jorge National Institute of Health (INSA) in Lisbon.
mutation rate “surprisingly high”
Virus evolution expert Richard Neher (Basel) explained that the mutation rate is “really surprisingly high”. The mutations would have a very specific pattern. The authors suspected that enzymes of the human immune system were responsible for these changes in the genome.
“We also see this accelerated mutation within the current epidemic. The rate is about one mutation per genome per month – with some uncertainty,” Neher said. Sars-CoV-2 has about two mutations per genome per month, but this genome is about seven times smaller. However, such comparisons of mutation rates do not make much sense and say little about the relative evolutionary variability of viruses.
When asked if mutations allowed the current spread at all, the scientist explained that, to his knowledge, there is no indication of that, but it cannot be ruled out. Most mutations “would probably not have dramatic effects.”
As Neher describes, many labs have now analyzed the genomes of monkeypox cases—most of these sequences belonged to the cluster described in the study.
About 5,000 cases of monkeypox in humans have been reported worldwide this year. In more than 40 countries outside Africa, where the disease was virtually unknown until May, there were 3,308 cases, according to data from the US health authority CDC as of just before midnight CEST on Wednesday.