(ORDO NEWS) — The monkeypox virus has mutated at a much faster rate than is normally expected and likely experienced a period of “accelerated evolution,” a new study says.
The virus, which has infected more than 3,500 people in 48 countries since it was discovered outside of Africa in May, may be more contagious due to dozens of new mutations.
In total, the virus carries 50 new mutations not seen in previous strains discovered between 2018 and 2019, according to a new study published June 24 in the journal Nature Medicine.
Scientists don’t usually expect viruses like monkeypox to get more than one or two mutations every year, the study authors note.
Monkeypox is a rare disease that virologists believe may naturally circulate among monkeys and rodents. Orthopoxvirus belongs to the same family and genus as variola virus and does not usually spread far beyond West and Central Africa, where it is endemic.
But this year, the first large-scale outbreak of the disease spread outside of Africa, surprising scientists and prompting the World Health Organization (WHO) to begin considering whether the outbreak should be classified as a global health emergency.
According to STAT, monkeypox virus strains can be divided into two clades, or lineages, known as the West African and Congo Basin clades. Each clade has a different mortality rate: the West African clade has approximately 1 percent mortality, while the Congo Basin clade kills about 10 percent of those infected.
The current outbreak appears to be caused by a West African hoard, according to STAT.
Being a large double-stranded DNA virus, monkeypox has a much greater ability to correct replication errors than an RNA virus like HIV, meaning that the current strain of monkeypox should have accumulated just a few mutations since it first started. circulate in 2018.
But by collecting DNA from 15 monkeypox virus samples and reconstructing their genetic information, the researchers found that the actual mutation rate was 6 to 12 times higher than they expected.
The huge jump in the mutation rate of the simian virus is “much larger than would be expected given previous estimates of the substitution rate for orthopoxviruses,” the researchers write in their paper. “Our data reveals additional signs of the ongoing evolution of the virus and potential adaptation to humans.”
Historically, monkeypox has been transmitted from person to person through close skin contact with open skin lesions, bodily fluids, contaminated materials, or respiratory droplets released into the air by coughing.
However, the unprecedented rate of new infections emerging may indicate that something has changed in how the virus infects its hosts – and new mutations could be a possible reason for this.
Many of the mutations the researchers have identified also contain indications that they may have come from the virus coming into contact with the human immune system, specifically the APOBEC3 family of virus-fighting enzymes.
These enzymes attack viruses, causing them to make mistakes in copying their genetic code, which usually results in the destruction of the virus.
However, sometimes the virus survives and simply introduces a few mutations into its genetic code, according to STAT. Perhaps such battles took place repeatedly and led to the fact that the virus acquired many mutations in a short period of time, the researchers suggested.
The mutation rate of the virus increased in 2018, and there are several explanations for why this happened.
Perhaps since then, the virus has been circulating in the human body at a low level, receiving many new mutations as a result of the struggle with enzymes.
Or the virus could have been spreading among animals in non-endemic countries without us noticing for quite some time, and then this year it suddenly spread to people.
Or it is possible that after the 2017 monkeypox outbreak in Nigeria, the virus spread mainly to African countries, evolving rapidly as it moved between small communities, and reappeared this year in non-endemic countries.
Despite its name, monkeypox is most commonly transmitted to humans by rodents, among which African rope squirrels, striped mice, giant rats and tailed porcupines are the main reservoirs of the disease, according to the Centers for Disease Control and Prevention.
The last time monkeypox was so widespread in the US was in 2003, when 71 people became infected with the West African variety after a shipment of infected Gambian rats brought to Texas from Ghana transmitted the disease to local prairie dogs.
A direct treatment for monkeypox has not yet been tested, but doctors inject patients with antiviral drugs and antibodies taken from people who have been vaccinated against smallpox.
Transmission is also reduced if people are vaccinated against smallpox or monkeypox, allowing scientists to prevent subsequent infections by inoculating close contacts of the first case – a strategy known as “ring vaccination” that led to the eradication of smallpox in the 1980s.
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