Covid-19: UK, South Africa strains spark a battle of mutations
South Africa’s health minister strongly rejected his British counterpart’s claim that a new coronavirus variant in the country is more contagious, sparking a battle over the Sars-Cov-2 mutations even as the United States said all travellers from the UK must present a negative Covid-19 test to avoid quarantine.
The unease over mutations in the virus -- first spotted in the UK before similar but distinct variants were seen in South Africa -- continued to spread to more parts of the world on Friday, with Germany, Switzerland and Japan saying they have identified their first cases. Earlier, Denmark, Netherlands, Australia and Belgium said they found the UK-linked variant.
These developments also come at a time when scientists are racing to uncover what implication the mutations will have on the pandemic and the vaccines.
“At present, there is no evidence that the 501.V2 (variant) is more transmissible than the United Kingdom variant -- as suggested by the British health secretary,” Zwelini Mkhize said in a statement. “There is also no evidence that [it] causes more severe disease or increased mortality than the UK variant or any variant that has been sequenced around the world,” he added.
He was responding to statement by Britain’s health secretary Matt Hancock on December 23 that said the variant in the African nation was “yet more transmissible and seemed to have changed even further”. In the case of both variants, scientists are yet to determine if the disease is more serious.
Around 50 countries have so far banned travel to and from the UK over concerns of the new variant. UK, in turn, has restricted travel from South Africa.
A preliminary mathematical modelling by researchers at London School of Hygiene and Tropical Medicine found that the variant – known as VOC 202012/01 -- is 56% more transmissible than other strains, and although there’s no clear evidence it results in more severe cases of the disease, higher number of cases could drive up more hospitalisations.
“We were unable to find clear evidence that VOC 202012/01 results in greater or lesser severity of disease than preexisting variants. Nevertheless, the increase in transmissibility is likely to lead to a large increase in incidence, with Covid-19 hospitalisations and deaths projected to reach higher levels in 2021 than were observed in 2020, even if regional tiered restrictions implemented before 19 December are maintained,” said the researchers.
Mutations are not unusual in viruses but a particular variant, reported first by authorities in the UK on December 14, has 17 changes that scientists say are an unusually high number. These include a change known as N501Y in the Spike protein, which is believed to make the virus bind to host cells more strongly.
The same change has been seen in two variants: one spreading in South Africa and another in UK’s Wales. Both of these variants have, however, appeared to have evolved separately, according to a phylogenetic analysis by Nextstrain.
The origin of the high number of changes in the UK-linked variant, also known as B.1.1.7, is as yet a mystery. A new threat assessment report by European Centers of Disease Control (E-CDC) said that as per “molecular clock estimates”, the Sars-Cov-2 has been mutating at a rate of two changes per month.
The VOC-202012/01, as compared to the variant that originated in Wuhan, has 29 changes, which makes a random evolution in an undetected part of the world unlikely. “...Random mutations acquired during circulation of the virus would not explain the unusually high proportion of spike protein mutations, and undetected circulation for a long enough time for the high number of mutations to accumulate (around 10 months according to current molecular clock estimates) is also not very likely due to global travel patterns,” the E-CDC said.
One of the theories supported by the E-CDC as well as authorities in the UK is that it evolved in a person with a compromised immunity. “One possible explanation for the emergence of the variant is prolonged Sars-CoV-2 infection in a single patient, potentially with reduced immunocompetence, similar to what has previously been described. Such prolonged infection can lead to accumulation of immune escape mutations at an elevated rate,” the E-CDC said.
Determining the origin of the variant will be crucial in order to prevent further mutations in the virus, which could have an implication for efficacy of vaccines. All major vaccine makers have said that at present, the changes do not appear to be significant enough to make their products obsolete.
Even if they do, vaccine makers will be able to make quick adjustments, said the CEO of BioNTech – the co-developer of the first coronavirus vaccine to be approved – last week.
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