Those returnees are residents of 14 different districts of the capital city.

The city has counted a total of 72,000 returnees from Da Nang, a tourism hotpot on the central coast that has become a Covid-19 hotspot since late July.

More than 58,000 have had their samples collected for the real-time polymerase chain reaction (RT-PCR) tests, the most trusted method for novel coronavirus testing now.

Of these, 28,000 have been confirmed negative and results of the rest are still pending.

According to the municipal Health Department, the incubation time for the virus is generally agreed as 14 days, but in reality, it has extended to between 23-34 days in some cases.

Therefore, as a guarantee measure, all people who have come into contact with people later diagnosed with Covid-19 or visited stricken areas should be tested even after they have completed their 14-day quarantine.

Since July 25, when community infections returned to Vietnam in Da Nang after a hiatus of more than three months, Hanoi has recorded 11 such cases.

Da Nang alone has recorded 354 infections. Community transmission of the virus has since spread to 14 other cities and provinces, including Hanoi and Ho Chi Minh City (eight cases).

The central city kicked off 15-day social distancing on July 28 and has extended it until further notice. Public transportation, including flights to and from the city of 1.1 million, has been suspended for the duration.

On August 12 and 13, four flights had carried 828 stranded visitors back to Hanoi, including 29 foreigners. All of them have been quarantined and tested.

In HCMC, nearly 3,000 people who returned from Da Nang in July have not reported themselves for quarantine or Covid-19 tests. The city authorities have threatened to impose criminal charges against those.