LONDON : A highly infectious variant of Covid-19 that has spread around the world since it was first discovered in Britain late last year is between 30% and 100% more deadly than previous dominant variants, researchers said on Wednesday.In a study that compared death rates among people in Britain infected with the new SARS-CoV-2 variant - known as B.1.1.7 - against those infected with other variants of the COVID-19-causing virus, scientists said the new variant's mortality rate was "significantly higher".The B.1.1.7 variant was first detected in Britain in September 2020, and has since also been found in more than 100 other countries.It has 23 mutations in its genetic code - a relatively high number - and some of them have made it far more.