A graphic created by researchers at the National Institute of Infectious Diseases shows genetic similarities in the first cluster infections of the coronavirus to that detected in Wuhan, China, while subsequent infections from March are genetically closer to the virus brought in from Europe. (Provided by National Institute of Infectious Diseases)

The spread of COVID-19 in Japan since March bears a similar genetic imprint to the new coronavirus that raged through Europe and caused many thousands of deaths, according to researchers at the National Institute of Infectious Diseases.

A study that involved analyzing the genome of the virus collected from about 560 patients confirmed to be infected by the coronavirus was compared with the genetic information of the coronavirus of about 4,500 individuals whose cases were registered in databases of other nations.

The analysis found that the virus detected in a number of initial cluster infections in Japan, as well as aboard the Diamond Princess cruise ship, was genetically similar to the one detected in Wuhan, China, where the outbreak is thought to have started in early January.

The study also found that the virus initially detected in Wuhan stopped spreading in Japan from about March and that there has been no further spread of that strain.

But the researchers said the coronavirus detected in Japan since March has genetic characteristics closer to the virus sweeping European nations rather than the Wuhan virus.

The researchers said there was a greater possibility that the coronavirus was transmitted in Japan through tourists to Europe as well as Japanese nationals who had returned home since March.