One patient is a 37-year-old Filipino education expert who flew from South Korea to Phu Quoc Island on July 19. She tested positive the next day and is being treated at the Phu Quoc District Medical Center.

The other three are Vietnamese, two men and a woman, aged 25-49. They had flown in from Russia to the Van Don Airport in northern Quang Ninh Province on July 17, and tested positive twice on Wednesday and Thursday. They are being treated at the Nam Dinh General Hospital in the northern eponymous province.

All four patients had been quarantined on arrival.

Sixteen others on the July 17 flight from Russia had tested Covid-19 positive previously.

All active Covid-19 cases in Vietnam are in stable health, and four have tested negative once.

Over 10,000 are in quarantine across the country, most of them in centralized facilities and the others in hospitals, own homes or other designated accommodations.

Vietnam has recorded no community transmission of the novel coronavirus in over three months.