Three types of the deadly coronavirus are spreading around the world – and the US is being rocked by the original strain from China.
Cambridge University researchers mapped the genetic history of the infection from December to March and found three distinct, but closely related, variants.
Analysis of the strains showed type A – the original virus that jumped to humans from bats via pangolins – was not China’s most common. Instead, the pandemic’s ground-zero was mainly hit by type B, which was in circulation as far back as Christmas Eve.
Results showed type A was the most prevalent in Australia and the US, which has recorded more than 400,000 COVID-19 cases. Two-thirds of American samples were type A – but infected patients mostly came from the West Coast, and not New York.
Dr Peter Forster and team found the UK was mostly being bombarded with type B cases, with three quarters of samples testing as that strain. Switzerland, Germany, France, Belgium and the Netherlands were also dominated by type B.
Another distinct variation, type C, descended from type B and spread to Europe via Singapore.
Scientists believe the virus – officially called SARS-CoV-2 – is constantly mutating to overcome immune system resistance in different populations.
The study has thrown up an oddity that the original A strain spread through West Coast USA despite not being being the most prevalent in China, the B strain.
However because both strains were in existence by January, when US got its first case, it does not mean it arrived any earlier and was not detected. The researchers said the study was too small to draw any firm conclusions.
The academics’ published work – which has been scrutinised by fellow scientists – only traced the samples of 160 patients across the world, including many of the first cases in Europe and the US.
Methods used to trace the prehistoric migration of ancient humans were adapted to track the spread of the SARS-CoV-2 virus, which causes COVID-19.
The team have now updated their analysis to include more than 1,000 COVID-19 cases up to the end of March to provide a clearer snapshot. It has not yet been peer-reviewed.
The smaller snapshot, published in the journal PNAS, initially suggested that type C was the most common in Europe.
But the data now shows type B is spreading more rampantly – all but one of 31 SARS-CoV-2 samples taken from patients in Switzerland were of the second cluster.
It comes after two separate genetic studies found most of New York’s outbreak came from Europe, and revealed the infection was being spread in mid-February – weeks before the city’s first confirmed case.
Researchers at Icahn School of Medicine at Mount Sinai NYU scientists studied DNA from thousands of samples of coronavirus patients to conclude travellers from Europe brought the virus to the Big Apple.
But they also found that the strand of the virus that arrived in Washington state came from China, echoing the finding of Dr Forster and team.
The Cambridge scientists found that two thirds of the 310 virus samples sequenced in the US were type A.
And all of the American cases linked to cruise ships had type B strains. It is not clear what ships they caught the virus on – but the Diamond Princess, quarantined off the coast of Japan for weeks, recorded more than 700 infections.
Data showed England’s first two cases – thought to be a University of York student and his mother at the end of January – had type A, suggesting they caught it in China.
No other samples from England, Scotland or Wales were type A, with almost 30 of the 40 viruses shown to be type B.
Dr Forster told MailOnline it was possible the UK’s outbreak could be traced back to Italy but that the data was too limited to make any conclusion.
The other cases recorded across Britain were type C, which is also likely to be traced back to East Asia.
The UK’s first ‘super-spreader’ – father-of-two Steve Walsh – was known to have went to a business conference in Singapore and infected scores of patients in Sussex.
Dr Forster told MailOnline that type A originally mutated into type B within China – but type C, the ‘daughter’ of B, evolved outside of the nation.
He admitted scientists are clueless as to how type B ‘pushed aside’ its predecessor to become more common in China – but the question will be answered ‘one day’.
Type B was found to be comfortable in the immune systems of people in Wuhan and did not need to mutate to adapt.
However, outside of Wuhan and in the bodies of people from different locations, the variation mutated much more rapidly.
This indicated it was adapting to try and survive and overcome resistance among other populations, such as Westerners.
Data analysis suggests the original strain of the virus could have been circulating in China as far back as September.
And Dr Forster said the type B strain was ‘alive and kicking’ by Christmas Eve, their analysis revealed.
It means the virus had already mutated before China recorded any COVID-19 cases – Wuhan first described an outbreak of a mysterious virus on December 31.
He told MailOnline: ‘The majority of cases in Wuhan are B type while a derived C type later emerged and spread initially via Singapore.’
And he suggested type C was not mutating – but called for caution over his finding, saying the sample was very small.
Dr Forster added that the data used was just a snapshot and did not include tens of thousands of confirmed cases recorded in each country.
For example, China’s outbreak may mainly consist of type A – but the data analysed suggests that is not the case.
Type A is the closest to the one found in bats and pangolins and is considered to be the ‘root’ of the outbreak.
Type A has two sub-clusters and the first, labelled as the T-allele, has substantial links to East Asia as it was found in Americans that lived in Wuhan.
However, the second A type sub-cluster, called the C-allele, is slightly different due to a string of mutations.
In the study, the scientists said: ‘Nearly half of the types in this subcluster, however, are found outside East Asia, mainly in the US and Australia.’
The original study had access to 93 type B genomes and 74 were in either Wuhan (22), other parts of eastern China (31) or neighbouring Asian countries (21).
A smattering were identified elsewhere, but type B had a strong affinity for Wuhan and is derived from type A via two mutations, at T8782C and C28144T.
The scientists argue that these methods could help predict future global hot spots of disease transmission and surge.
By JOE PINKSTONE
Source: dailymail.co.uk
