The prevalence of Beta across the world has dropped over the course of 2021 at the same time that the highly-transmissible Delta variant has taken hold, data show
The Beta variant of coronavirus is likely to fade away in the coming months due to the dominance of Delta, scientists have predicted.
Data shows that the global prevalence of Beta has dropped over the course of 2021 as the highly-transmissible Delta variant, which is also capable of partially evading the Covid vaccines, continues to surge in multiple countries.
Information on genetically sequenced cases – which allows scientists to determine which type of Covid variant has caused a patient’s infection – is uploaded in each country to a number of publicly available sources, including the Global Initiative on Sharing All Influenza Data (Gisaid).
Not all data is always shared, and many countries lack the technology to carry out genomic genomic surveillance, but Gisaid’s figures show that very few countries are now detecting Beta, which first emerged in South Africa late last year.
Between 15 和 21 行进, a record high of 1,956 sequenced Beta infections were reported globally to Gisaid, out of a total of shared 91, 644 案例.
This suggests that around 2 per cent of all the world’s cases were caused by Beta in mid-March – though this is likely to be an underestimate due to the limited surveillance networks of most countries.
经过 11 七月, 只是 0.4 per cent of sequenced cases reported to Gisaid were Beta.
同时, Delta accounted for 70.4 per cent of all sequenced cases, having previously made up just 0.1 per cent of infections in mid-March. Its dominance has similarly led to a fall in worldwide Alpha cases.
There are outliers in the data, 然而, with some countries recording a recent rise in Beta infections. In the past four weeks, 西班牙, France and South Africa have reported 148, 79 和 22 new cases of the variant respectively, according to Gisaid.
尽管如此, scientists are confident that Beta is being comprehensively outcompeted by Delta and, in some parts of the world, edging towards extinction.
“Beta is really good at escaping the vaccines but unlike Alpha and Delta, it doesn’t have – or at least nobody has demonstrated yet – a particularly strong transmission advantage,” said Aris Katzourakis, a professor of evolution and genomics at Oxford University,
“所以, it’s likely to be outcompeted by both Alpha and Delta in vaccine-naive populations. It’s not surprising that it is happening.”
The Beta variant, formerly known as B.1.351, contains several mutations in its ‘spike’ protein – the part of the virus that attaches to human cells and gains entry.
This includes the E484K mutation which appears to help the virus partially evade antibodies and reduce the protection generated by the current generation of vaccines.
One study conducted in February showed that Beta lowered the efficacy of the AstraZeneca vaccine to just 10.4 百分.
But it’s inability to transmit as well as both the Delta and Alpha variants in largely unvaccinated populations means it has struggled to gain a foothold.
“When viruses jump hosts [from animals to humans] it throws off a huge number of variants,” said Professor Paul Hunter, an expert in health protection and infectious diseases at the University of East Anglia. “They evolve very rapidly and it’s try to get the best fit with the new host.
“Once it’s got a combination which is the best fit – think of it as a key in the lock – then that variant takes over and effectively excludes all the other variants.
“After that point you still get some evolution but it’s a lot slower. I think the Beta variant was one of these half-hearted attempts at getting the best fit for the key.”
Prof Hunter suggested that Beta could become extinct in a year’s time or “hang around in some long forgotten corner of the planet”.
Jonathan Ball, a professor of molecular virology at the University of Nottingham, said that the Beta variant is a “bit of a lightweight” in terms of its “general fitness”.
然而, the scientists acknowledged that circumstances could change in favour of the Beta variant if and when vaccination rates across the world improve.
In a population with high coverage, Beta’s advantageous E484K mutation – along with the other changes it has acquired in its genome – could play a greater, more influential role.
“Because of the changing selective landscape, it could have a relative competitive advantage in a highly vaccinated population,” said Prof Katzourakis.
“It’s conceivable that once we vaccinate enough people that it could start to increase in relative prevalence – 然而, not at the rate at which Delta sweeps through a population.
“It’s likely that the combination of transmission advantage and vaccine escape might always give Delta the edge.”