Scientists fear an even more contagious strain of monkeypox could emerge as the tropical virus continues to mutate and spread among people.
Researchers in Britain said the virus was now mutating “much faster” than in 2018, when only isolated cases were detected.
Their analysis found that mutations mainly targeted a gene that attacks the human immune system to prevent the virus from mutating, allowing it to evade immunity.
The team also suggested that monkeypox, or mpox, had been circulating among humans since 2016 – or six years before the current outbreak.
The above graph shows mpox infections in the US in 2022, as the country faced an outbreak of the tropical virus
And above that are the cases recorded in 2023. They are far below the numbers they were
The above map shows the number of monkeypox cases detected by state in 2022 and 2023
The authors, from the University of Edinburgh, wrote in the paper: ‘Although the B.1 lineage has now been reduced across the world – although not yet eradicated – the human epidemic from which it emerged continues unabated.’
They added: ‘These observations of persistent Mpox transmission present a fundamental shift in the perception of Mpox… as a (animal-to-human spillover).
‘They highlight the need for a review of public health messaging around mpox, as well as outbreak management and control.’
As a virus spreads between people and makes more copies of itself, it increases the risk that new mutations will emerge, which could make the strain more transmittable or more dangerous.
In their research, published in the journal Scienceresearchers compared mpox sequences from 2018 to 2022 and found that the number of mutations had increased rapidly, which they said suggested “sustained human-to-human transmission.”
They found that the mutations were concentrated in the region of the genome targeted by the human immune system enzymes, known as APOBEC3.
These are able to change bases within a genetic code, inhibiting a virus’s ability to reproduce.
The scientists said the repeated changes to this gene also signaled ongoing human-to-human MPox transmission rather than repeated spillover events.
Their molecular clock used the B.1 lineage of mpox, the type behind the ongoing outbreak among humans.
Mpox has historically been endemic to West and Central Africa, causing only sporadic cases when the virus was transmitted via rodents.
But in 2022, an international epidemic emerged that led to 30,000 cases and 55 deaths in the US alone, with California, New York and Texas hardest hit.
Globally, there are more than 64,000 infections in 100 countries – including Britain, Spain and Germany.
A massive public health response was launched in the US, introducing vaccines to those most at risk, such as gay or bisexual men with multiple sexual partners.
Contact tracing efforts were also underway to break the chains of transmission.
The measures were largely successful and the surge in cases subsided.
But sporadic infections have continued to emerge in 2023, suggesting the disease is still circulating under the radar.
People can become infected with MPOX through touching infectious sores or lesions on patients.
Some doctors have also suggested that monkeypox can be contracted by breathing the air of someone who has infectious lesions in the throat, although they emphasize that these cases are extremely rare.
Most infections are mild and can be treated with antiviral drugs and by isolating patients until symptoms resolve.
In severe cases, however, the disease can lead to complications, including encephalitis – or inflammation of the brain – and heart and eye problems.
The data shows that the US has detected 935 cases in 2023 as the virus continues to emerge in the country.
Mpox has been established for decades in parts of Central and West Africa, where people are mainly infected by animals such as wild rodents.
But the disease was not known to cause major outbreaks outside the continent or spread easily among people until last May, when dozens of epidemics emerged in Europe, North America and elsewhere.
Mpox usually causes symptoms such as rash, fever, headache, muscle pain and swollen lymph nodes.
The skin lesions can last up to a month and the disease is spread through close physical contact with an infected patient or through their clothing or bedding.
Most people are offered antiviral drugs and painkillers to help with recovery, and they are also told to spend time at home.
Scientists ultimately concluded that the unprecedented outbreak was linked to sex among gay and bisexual men at raves in Spain and Belgium, marking a significant departure from the typical pattern of spread of the mpox in Africa, where outbreaks do not spread across borders have spread.