COPENHAGEN: One in five new coronavirus cases in Denmark was infected with the more contagious British variant in the last week of January, preliminary data showed on Friday, prompting experts to say lockdown restrictions were still necessary to curb the epidemic.

Denmark instituted hard lockdown measures in December after seeing infections rise exponentially and in particular to curb the spread of the new B.1.1.7. variant, first identified in Britain.

The variant, which Danish authorities say could be up to 50% more infectious, is expected to be the dominant one by mid-February.

Denmark has registered just over 200,000 infections in total, with 2,200 corona-related deaths. But general infections numbers are one the decline. From thousands of daily infections in December, only 438 cases has been registered in the last 24 hours.

"We are down to some very low infection rates and if it were not for the darned B.1.1.7., we would be able to relax," associate professor of mathematical epidemiology at Roskilde University, Viggo Andreasen, told Reuters.

The share of positive tests, which had the new variant, has risen from 4% in the first week of January to 19.5% in the fourth week, the State Serum Institute (SSI) said in a report on Friday.

An average of 49% of positive tests have been analysed for their genetic material this year.

"Many people don't understand why we don't open our society," immunology professor at Copenhagen University Jan Pravsgaard Christensen told Reuters.

"And that's because those that are becoming infected now, are infected with a more transmissible virus."

Just 300-400 people carrying the mutated variant is too many and could lead to explosive infection rates if lockdown restrictions are eased too early, Christensen said.

The weekly infection rate for the new variant has slowed though, according to Andreasen, and with the current restrictions in place it will not cause a new spike in infection rates, he said.