French experts said that they have spotted the 'Breton' Covid variant which 'may fully evade tests' but the mutant strain is no deadlier or more transmissible than the original virus.

Iran PressEurope: Eight cases of the 'Breton variant' were detected in a hospital in Lannion, a town in the northwest region of Brittany. 

The French health ministry revealed that despite being infected with the virus, the patients' polymerase chain reaction (PCR) test results were negative. They were only spotted through genomic sequencing of the samples.

It's thought to be the first time any variant has slipped past the gold-standard PCR tests, which are critical for keeping track of the pandemic. 

While PCR cannot diagnose other variants, including Brazil and South African versions, it still gives a Covid positive result. 

Scientists at the Institut Pasteur who discovered the Breton variant said it does not appear to be more transmissible or deadly than the original virus.

They revealed the new strain carries nine mutations on its spike protein, but also in 'other viral regions'. They did not provide any further details.

The experts will carry out further research to work out what effect the variant will have on vaccines.  

The emergence of the new strain comes as France suffers rising infection rates and faces calls for another lockdown. The country is recording 20,000 new cases every day.