The hospital, one of Vietnam’s largest, has been locked down since Saturday morning. The first two cases at the hospital, two nurses, were confirmed positive on March 20. As of Thursday, 40 Covid-19 cases linked to the hospital have been confirmed.

The hospital’s emergence as the nation’s largest infection hotspot has prompted many localities to search for residents who had visited it since March 10.

Most people who’ve visited the hospital have come from the north of the country, and a few have been identified in central Vietnam.

In the northern province of Nam Dinh, about 2,610 people visited the hospital between March 12 and 27. Of these, 308 people received inpatient treatment, while the remainder went for a check up and left the same day.

Bui Thi Minh Thu, director of the Nam Dinh Health Department, said the province is planning a campaign to quarantine everyone who has visited the hospital and those who’d had close contact with them.

The province had also sent 31 officials to the Bach Mai Hospital for a study trip. Twenty have returned and are being quarantined at home and the others are still in Hanoi.

In another northern province, Hai Duong, nearly 2,390 people visited the hospital between March 10 and 27. 250 received inpatient care. The inpatients have returned and have been isolated, and samples have been taken from half of them for testing.

Pham Manh Cuong, director of the Hai Duong Health Department, said the province had only found 1,500 people as of Monday.

Thai Binh, yet another northern province, has recorded 1,030 residents as receiving outpatient treatment and 125 being inpatients at Bach Mai during the period under consideration. Thirty-five people have so far been quarantined in the province. Local health officials said that the number of visitors to the Bach Mai Hospital is very large. They are scattered everywhere throughout Thai Binh, making it a challenge for the authorities who are still in the process of identifying them.

In the northern province of Ninh Binh, 616 people visited the hospital between March 15 and 26, according to Vu Manh Duong, director of the provincial health department. 225 are awaiting Covid-19 test results and the others are being placed in a centralized quarantine area.

In Yen Bai, 321 people have been identified and 253 quarantined at home. Fifty-seven have already completed a 14-day mandatory home quarantine stint. Eleven others are at isolation facilities in the province.

The province has taken samples from 181 people. Of these, 85 have tested negative for the coronavirus and results for the remaining are pending. The province is also collecting samples of everyone associated with the hospital and those who’d come in contact with them.

One of Hanoi’s neighbors, Vinh Phuc Province, has identified more than 1,000 people who’d been to the hospital, said Nguyen Thanh Hai, director of the provincial health department. They have been isolated from the community and their samples are being tested.

"Because the province is right next to Hanoi, we have also asked local authorities to search for taxi drivers who took people to the hospital," Hai said.

Elsewhere in the northern highlands, the provinces of Lang Son, Ha Giang, Hoa Binh and Tuyen Quang have respectively identified 236, 106, 441 and  270 resident with links to Bach Mai and isolated them at home. Some have got their samples tested, but the results are not known yet.

In central Vietnam, Da Nang City authorities are still searching for Bach Mai Hospital visitors. Ten residents who visited the hospital and several doctors and apprentices who went there to study have tested negative for the virus, said Ton That Thanh, director of Da Nang Center for Disease Control.

"We are waiting for local authorities to compile a specific list [of people] so samples can be taken for testing, and to ensure every visitor to the Bach Mai Hospital is monitored," Thanh said.

In Quang Nam Province, Da Nang's neighbor, seven people have been identified, including patients, doctors and people who visited family members being treated at the Bach Mai Hospital. Everyone has been quarantined at home and some have had their samples tested. Results are unknown at this point.

Other northern and central localities including Thanh Hoa, Nghe An, Hai Phong, and Quang Ninh have identified and are monitoring over 4,600 people.

Of the 222 Covid-19 patients confirmed in Vietnam until now, 64 have been discharged from hospitals.

Most of the active cases are those who have returned from Europe and the U.S. and people who’ve had close contact with them.

The Covid-19 pandemic has spread to 203 countries and territories, claiming over 47,000 lives.