The monkeypox virus mutated much faster than would otherwise be expected and probably went through a period of “accelerated evolution,” a new study suggests.
The virus, which infected more than 3,500 people in 48 countries since it was discovered outside Africa in May, it could be more contagious due to dozens of new mutations. In total, the virus carries 50 new mutations not seen in previous strains detected from 2018 to 2019, according to a new study published June 24 in the journal Nature medicine (opens in new tab). Scientists don’t usually expect it viruses like monkeypox get more than one or two mutations each year, the study authors noted.
Smallpox is a rare disease that virologists believe can circulate naturally in monkeys and rodents. The orthopoxvirus, comes from the same family and genus as the smallpox virus, which causes smallpox, and does not usually spread far beyond West and Central Africa, where it is endemic. This year, however, the first widespread outbreak spread beyond Africa, surprising scientists and prompting the World Health Organization (WHO) to begin considering whether to classify the epidemic as global health crisis.
Strains of monkeypox virus can be classified into two logs, or lineages, known as West African and Congo Basin logs, according to STAT. The viruses in each cluster carry different mortality rates; the West African log has approximately 1% mortality, while the Congo Basin log kills about 10% of those infected. The ongoing epidemic appears to have been triggered by West African descent, STAT reported.
Related: Outbreaks of monkeypox: Here’s everything you need to know
Like a big double chain DNA viruses, monkeypox are much more capable of correcting replication errors than viruses RNA viruses such as HIV, meaning the current strain of monkeypox should actually have accumulated only a few mutations since it first began circulating in 2018. But after collecting DNA from 15 samples of monkeypox virus and reconstructing their genetic information, the scientists found that the true mutation rate was six to 12 times higher than they expected.
The huge jump in the monkey virus mutation rate “is far more than would be expected given previous estimates of the replacement rate for orthopoxviruses,” the researchers wrote in the paper. “Our data reveal additional indications of ongoing viral evolution and potential human adaptation.”
Historically, monkeypox has been transmitted from person to person through close skin contact with open skin lesions, body fluids, contaminated material, or respiratory droplets that cough up air. But the unprecedented rate of new infections could suggest that something may have changed about the way the virus infects its hosts – and new mutations could be a possible cause.
Many of the mutations identified by researchers also carry treacherous clues that may have occurred due to virus contact with humans immune system, more specifically a family of enzymes that fight viruses called APOBEC3. These enzymes attack viruses forcing them to make mistakes when they copy their genetic code, which usually causes the virus to break down. However, sometimes a virus survives an encounter and simply picks up a few mutations in its genetic code, according to STAT. It is possible that such battles were repeated and caused the virus to pick up many mutations in a short period of time, the researchers theorized.
The mutation rate of the virus increased in 2018, and there are several explanations for why it did so. It is possible that the virus has since circulated to humans, at low levels, raising a number of new mutations through its battles with enzymes. Alternatively, the virus may have been spreading among animals in non-endemic countries for some time without us noticing, and then it suddenly returned to humans this year.
Or it is possible that, after the monkeypox epidemic hit Nigeria in 2017, the virus spread mainly in African countries – it developed rapidly as it moved between smaller communities before it began to recover again this year in non-endemic countries.
Despite their name, monkeypox is most commonly transmitted to humans from rodents, of which African squirrels, striped mice, giant bag rats, and brush-tailed porcupines are believed to be the main reservoirs of the disease, according to the Centers for Disease and Prevention.
The last time monkeypox was so prevalent in the United States was in 2003, when 71 people became infected with West African logs after a shipment of infected Gambian rats in bags, imported to Texas from Ghana, transmitted the disease to local prairie dogs.
Direct treatment for monkeypox has yet to be tested, but doctors are giving patients antiviral drugs and antibodies taken from people vaccinated against the smallpox vaccine. Transmission is also reduced if humans have a vaccine against monkeys or smallpox, which allows scientists to prevent further infections by vaccinating close contacts of the initial case – a strategy known as “ring vaccination” that led to the eradication of smallpox in the 1980s.
Originally posted on Live Science.
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