The move came just one day after Vietnam detected 93 community transmissions, mostly in Hai Duong and Quang Ninh, following 57 clean days. Hundreds of medical experts have been sent to the outbreak areas for contact tracing and mass testing to prevent the virus from spreading.

Medical facilities are required to cooperate with disease control centers or hospitals capable of testing for Covid-19 using Realtime RT-PCR to collect samples from all medical staff for screening, deputy health minister Nguyen Truong Son said in the directive.

Hospitals are also required to take samples of all patients in departments of emergency, emergency resuscitation, intensive care and random samples of at least 30 percent of inpatients in the remaining departments for coronavirus testing to early detect potential Covid-19 cases.

During the Covid-19 outbreak in Da Nang City in July last year, a series of hospitals were determined coronavirus hubs, leading to a number of medical workers and in-patients, including those in critically-ill condition, being infected with the virus.

Hai Duong is now the biggest hotspot with 77 cases, followed by Quang Ninh with 13 cases, with one each in Hanoi, Bac Ninh and Hai Phong. Hai Duong’s Chi Linh Town, with around 220,000 residents, has been put under lockdown for 21 days starting Thursday noon.

Infections in Hai Duong are linked to a 34-year-old Vietnamese woman who flew to Japan last week and tested positive there for the coronavirus variant that originated in the U.K. and is believed to be 70 percent more contagious than other strains.

So far, 1,651 cases have been recorded nationally, with 35 deaths.