"Today we discovered Colorado's first case of the COVID-19 variant B.1.1.7, the same variant discovered in the UK," Colorado Governor Jared Polis said on Twitter.

The Colorado identification is the first known case in the US.

British Prime Minister Boris Johnson says the variant of the coronavirus, which could be up to 70 per cent more transmissible, is spreading rapidly in Britain.

A separate variant, first found in South Africa, is also causing concern.

Health authorities around the world have been reporting cases of the new variants.

* SWITZERLAND has documented five cases of the variant from Britain and two of the South African mutation, a health ministry official said on Tuesday.

* DENMARK has identified 33 infections with the variant spreading in Britain, authorities said on December 24.

* FRANCE, which has the highest number of cases in the European Union, recorded its first of a variant in a Frenchman arriving back from London.

* INDIA has found six cases of a variant on a flight from Britain and is likely to extend a flight ban to guard against it.

* JAPAN on Monday detected the variant found in South Africa, the government said, the first such discovery in a nation that has already identified more than a dozen cases of the variant which is spreading in Britain.

* SOUTH KOREA said the UK variant was found in three people who had entered South Korea from London on December 22.

* NORWAY said the variant circulating in Britain had been detected in two people who arrived from the UK.

* AUSTRALIA said two arrivals from the UK were carrying the British variant.

* JORDAN has detected its first two cases of the UK variant. The kingdom last week banned flights to and from Britain until January 3.

* GERMANY said the variant from Britain had been found in a passenger flying to Frankfurt from London on December 20. It seems to have been present in Germany since November, the Die Welt newspaper reported on Monday.

* ITALY detected a patient infected with the UK variant, the health ministry said on December 20.

* The variant linked to Britain has been detected on the island of Madeira in PORTUGAL, the regional civil protection authority said.

* Health officials in FINLAND said the UK variant has been detected in two people, while the South African mutation has been detected in one.

* SWEDEN said the variant circulating in Britain had been detected after a traveller from the UK fell ill on arrival and tested positive.

* Officials in CANADA said that two confirmed cases of the UK strain had appeared in Ontario.

* CHILE said on Tuesday it had recorded its first case of the British variant, prompting health authorities to reinstate a mandatory quarantine period for all visitors.

* IRELAND on Christmas Day confirmed the presence of the British variant.

* LEBANON detected its first case on a flight arriving from London.

* UNITED ARAB EMIRATES discovered a "limited number" of cases of people infected with a new variant, a government official said on Tuesday.

* SINGAPORE confirmed its first case of the UK variant, the patient arriving from Britain on December 6, while 11 others who were already in quarantine had returned preliminarily positive results for the new strain.

* ISRAEL detected four cases of the virus emerging in Britain. Three of the cases were returnees from England.

* The variant spreading in Britain appears to have infected two students who returned to HONG KONG from the UK, the Department of Health said last week.

* PAKISTAN health officials said on Tuesday the variant found in Britain had been detected in the southern province of Sindh.

* And yet another variant of the coronavirus may have emerged in NIGERIA, the head of Africa's disease control body said, cautioning that more investigation was needed.

The World Health Organization (WHO) says there is not enough information to determine whether the new variants could undermine vaccines being rolled out internationally.

Australian Associated Press