The new mutant strain, which is partly similar to different variants reported in the U.K. and South Africa, was detected in four infected people who arrived from Brazil, the ministry said.
The National Institute of Infectious Diseases (NIID) said there was no evidence at present that the new variant was highly infectious, but it was investigating whether it could cause severe symptoms and whether or not it is resistant to vaccines.
Of the four people, a man in his 40s showed no symptoms upon arrival, but later developed breathing difficulties and was hospitalized, the ministry said. A woman in her 30 has symptoms such as headache. A male in the 10-19 age group has a fever, while a woman in the same age group is free of symptoms.
