"Patient 1216," 41, returned to Vietnam on October 19 on Vietnam Airlines flight VN8 that touched down in Van Don airport in northern Quang Ninh Province.
She was sent to centralized quarantine upon entry at a military facility in Bac Ninh Province. Her first two tests were negative but the third one on Monday arrived as positive.
Previously, 17 passengers on the same flight have been diagnosed with Covid-19. They are undergoing treatment in northern Bac Giang and Bac Ninh provinces.
The latest patient has raised Vietnam's Covid-19 tally to 1,216. Of them, 1,087 have recovered and 35 died. Three died after having been confirmed to recover from Covid-19 and therefore were neither listed as Covid-19 deaths or recoveries.
Of the total cases registered in Vietnam, 691 are locally transmitted and the rest are all Vietnamese returning from abroad or foreigners visiting Vietnam.
For more than two months, the nation has not recorded any community transmission. It is putting more than 15,000 in quarantine.
Almost 1.27 million have died of Covid-19 around the world in more than 50 million confirmed cases.