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 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 genetic history of the coronavirus was mapped from December 24 to March 4, revealing three distinct, but closely related, variants. Scientists believe the virus may be constantly mutating to overcome differing levels of immune system resistance in different populations
Pictured, a breakdown of the different coronavirus genomes and to which of the three major group they belong to. The lines indicate a rough split between the type. The larger the circle, the higher the amount of cases
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 It has not yet been peer-reviewed.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 a separate genetic analysis 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.
Methods used to trace the prehistoric migration of ancient humans was adapted to track the spread of the SARS-CoV-2 virus, which causes COVID-19
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.
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 – 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.
Dr Forster told MailOnline that both type A and type B strains have mutated within China – but type C evolved outside of the nation.
DNA Researchers believe the virus was being spread around the city by mid-February – weeks before New York’s first confirmed case. This map is based on an earlier based on an earlier genome study and shows eight different strains of coronavirus identified by scientists and how they have spread around the world
Travel data shows 3.4 million travelers from countries that would end up hardest-hit by the coronavirus outbreak entered the US as the pandemic was starting
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’.
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.’
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.