The coronavirus mutation first found in Britain has now spread to 50 territories, according to the World Health Organization, while a similar South African-identified strain has now been found in 20. The UN body also noted a third new coronavirus "variant of concern" found in Japan may impact upon immune response and needs further investigation.

"The more the SARS-CoV-2 virus spreads, the more opportunities it has to change. High levels of transmission mean that we should expect more variants to emerge," the WHO said. Since first being reported to the WHO on December 14, the British-identified variant VOC 202012/01 has been found in 50 countries, territories and areas, the agency said.

Test results showed the age and sex distribution was similar to that of other circulating variants, while contact tracing data revealed "higher transmissibility where the index case has the variant strain". The South African-identified variant 501Y.V2, first reported on December 18, has now been detected in 20 countries, territories and areas.