Photo/Illutration A quarantine officer receives saliva samples from an entrant to Japan to conduct an antigen test for the novel coronavirus at Narita Airport in Chiba Prefecture on May 23. (Yasuhiro Sugimoto)

The government is preparing to strengthen border controls on entrants to Japan arriving from Vietnam starting on June 4 at the earliest amid reports of a new hybrid strain of the novel coronavirus detected there.

The government is considering asking travelers arriving from Vietnam and Malaysia, which has also been hit by a surge in infections from virus variants, to stay at designated quarantine facilities for six days.

The Vietnamese government described the hybrid of Indian and British variants as “much more transmissible when airborne than other variants.”

“We would like to implement necessary measures flexibly and promptly to alleviate people’s anxiety,” Chief Cabinet Secretary Katsunobu Kato said at a news conference on May 31.

Arrivals from India, Pakistan, Nepal, Bangladesh, Maldives and Sri Lanka are currently required to self-isolate at designated accommodation facilities for 10 days. The government is also considering adding Afghanistan to the list of that measure as early as June 4.