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Monkeypox is mutating fast

July 4, 2022

New research suggests that monkeypox is mutating surprisingly fast in Europe and North America. The study shows how little we know about the virus.

A skin rash caused by the monkeypox virus, seen here under a microscope
The genetics of the virus that causes monkeypox are relatively unknown. This is the kind of skin rash that the virus causes, viewed under a microscope.Image: CDC/REUTERS

The monkeypox virus spreading across the US, Europe and the UK is mutating surprisingly fast, according to a study conducted by Portuguese researchers and published in the journal Nature Medicine. The study offers the most in-depth look at the genetic makeup of the virus so far.

Scientists sequence virus genomes because the genome is the virus's playbook — the genome is the genetic material of an organism, and, in the case of a virus, it tells us what the virus is, what is does and how it is likely to spread.

Monkeypox mutated 50 times since 2018

For the study, the researchers took samples from 15 monkeypox patients and compared the genomes of the virus that had infected them.

The researchers found that the patients each had a strain of monkeypox that could be traced back to a previous outbreak of the virus in 2018-2019 in the United Kingdom, Israel and Singapore, which had originated in Nigeria.

But, more than that, the tests showed that the virus had mutated 50 times — up to 12 times more than they would have expected — since that previous outbreak in 2018.

"This data completely challenges what is known about the mutation rate of monkeypox," said study author Joao Paulo Gomes, a researcher at Portugal's National Health Institute.

West African monkeypox has lower death rates

There are a few things we know about monkeypox, and this new genome sequencing has helped researchers understand the current outbreak better.

First, the strain of the virus in the current outbreak is mutating at an unusually fast rate.

Second, the outbreak probably started with a single case infecting others at a large superspreader event.

The strain is part of the West African clade of monkeypox, which is commonly reported in western Cameroon and Sierra Leone and carries a mortality rate lower than 1%.

A clade is defined as a group of organisms that can be traced back to common ancestors or a common genetic lineage. 

There is another common clade of monkeypox, known as the "Central African" clade, which is more present in the Congo basin and sees death rates of up to 10%.

Monkeypox Virus up close
There are two main "clades" of the monkeypox virus. The clade currently circulating in Europe and the United States is the less deadly of the two, with a fatality rate of about 1%.Image: BSIP/CDC/SGO/picture-alliance

The monkeypox incubation period makes it hard to track

There is also a lot more we don't know about monkeypox in this current outbreak.

Its incubation period, which ranges from five to 21 days, makes its movement hard to track.

The World Health Organization has identified the "index case" — the first confirmed case — as a person who traveled from Nigeria to the United States in early May.

But the researchers in Portugal dispute that idea because, they say, there were confirmed cases in Portugal and the United Kingdom in late April.

If the researchers in Portugal are correct, we know less than we thought about the current outbreak, including how it has evolved and what it is likely to do next.

So where did the monkeypox outbreak start?

The scientists write in their study paper that it is very likely the virus was imported from a country where monkeypox is endemic, such as Nigeria, but they say they cannot rule out other possibilities.

They say it is also possible, for example, that the virus spread silently through humans and/or other animals in nonendemic countries such as the UK or Singapore after the 2018-2019 outbreak.

And, they say, it's unclear whether the mutated version is any worse than the original version.

"The authors describe an unexpectedly high number of mutations in the virus, but their implications for disease severity or transmissibility are unclear," Hugh Adler, a researcher at the Liverpool School of Tropical Medicine, said in response to the paper. He was not involved with the research.

"We have not identified any change in the severity of clinical disease in patients diagnosed in the current outbreak," said Adler, who has worked with monkeypox patients in the United Kingdom during previous outbreaks.

Monkeypox research is 'still in its infancy'

Monkeypox is a double-stranded DNA zoonotic virus. DNA viruses mutate slower than RNA viruses, such as the one that causes COVID-19. 

But we generally lack a lot of knowledge about monkeypox. The researchers in Portugal, for instance, cite only a single other study on the genetics of the virus.

Monkeypox symptoms, like red dots, seen on skin
Monkeypox symptoms can manifest on the skin in the form of small red dots, but can also include flulike symptoms such as headache and sore throatImage: Institute of Tropical Medicine/dpa/picture alliance

Adler said the study of the virus's genetics was "still in its infancy."

"We have the genome sequence, so we have an idea of what the genes are," Adler said. "But, in terms of really understanding what they do and the implications for evolution, if the genes change — there's very little research done on that compared to a lot of the other big viruses that we know."

Adler said the research by Gomes' team in Portugal had provided "fascinating" new insights into the biology of monkeypox, but Adler noted that it looked like the study had only occurred because of the virus's current spread in high-income countries.

"As ever, if the global community had applied these same scientific resources to monkeypox outbreaks in Africa, we might already have a stronger knowledge base," Adler said.

Monkeypox was first discovered in a monkey in 1958, and the first human case was found in a small child in 1970 in the Democratic Republic of the Congo.

COVID-19 and monkeypox: Similar but different

Edited by: Zulfikar Abbany

Clare Roth
Clare Roth Editor and reporter focusing on science and migration