Hanoi is entering a more intense phase of the fight against the coronavirus and it challenges the city's efforts if secondary transmission is not well managed.

Vietnam is warned that if authorities fail to identify people who potentially carry the coronavirus, secondary transmission might be serious in the coming days.

Six out of 11 the newly-detected cases are from Ho Chi Minh City.

To be considered healthy, Covid-19 patients need to test negative for the virus three consecutive times and go through quarantine for two weeks.