A coronavirus variant that originated in Spanish farm workers has spread rapidly through much of Europe since the summer and now accounts for the majority of new Covid-19 cases in several countries –  and more than 80 percent in the UK.  An international team of scientists that has been tracking the virus through its genetic mutations has described the extraordinary spread of the variant, called 20A.EU1, in a research paper to be published on Thursday.

Their work suggests that people returning from holiday in Spain played a key role in transmitting the virus across Europe, raising questions about whether the second wave that is sweeping the continent could have been reduced by improved screening at airports and other transport hubs. Because each variant has its own genetic signature, it can be traced back to the place it originated.

“From the spread of 20A.EU1, it seems clear that the [virus prevention] measures in place were often not sufficient to stop onward transmission of introduced variants this summer,” said Emma Hodcroft, an evolutionary geneticist at the University of Basel and lead author of the study which is yet to be published in a peer-reviewed journal.

The scientific teams in Switzerland and Spain are now rushing to examine the behavior of the variant to establish whether it may be more deadly or more infectious than other strains.

Dr Hodcroft stressed that there was “no evidence that the variant’s [rapid] spread is due to a mutation that increases transmission or impacts clinical outcome”. But she emphasised that 20A.EU1 was unlike any version of Sars­ Cov-2 – the virus that causes Covid-19 – she had previously come across. “I’ve not seen any variant with this sort of dynamic for as long as I’ve been looking at genomic sequences of coronavirus in Europe,” she said.