Covid 19 coronavirus: New mutant coronavirus strain discovered in Japan

The Japanese Health Ministry has found a coronavirus variant in people arriving from Brazil that's different from the ones in Britain and South Africa.

The variant was found in airport tests on a man in his 40s, a woman in her 30s and two teens, the ministry said on Sunday (Japan time).

According to Nikkei Asia, the passengers landed at Haneda Airport in Tokyo on Saturday, January 2.

A man walks through an alley filled with restaurants and bars on the first day of a coronavirus state of emergency in Tokyo. Photo / AP

Japan was working with other nations, the World Health Organisation and other medical experts to analyse the new version of the virus, and it was still unclear whether available vaccines would work.

The man who tested positive had no symptoms upon arrival but was hospitalised after his breathing became difficult. The woman suffered headaches, one teen, a male, had a fever, while the other female teen had no symptoms, according to the ministry.

About 30 cases of variants from Britain and South Africa have earlier been reported in Japan. Experts are worried the variants appear to spread faster.

A woman looks at strawberries at a supermarket on the first day of a coronavirus state of emergency in Tokyo. Photo / AP

Japan has declared a state of emergency for the Tokyo area, which kicked in Friday, asking restaurants and bars to close at 8pm. Some have complained that's not enough, noting train stations and eateries are still packed, including at night.

Japan has had about 4000 deaths related to Covid-19 so far, and more than 280,000 confirmed cases.