Two positive cases at Japanese optical-imaging firm Canon Vietnam are both linked to a co-worker who was tagged as "patient 3357" on Monday.

The two new cases have not been confirmed as Covid patients, pending further test results.

"Patient 3357" had traveled with another coronavirus patient on a van to Hanoi to receive goods on May 3.

From May 4 to May 6, he continued working at a factory of the firm. On May 5 he visited a local kindergarten and met with some teachers who worked there. The teachers have now been put into centralized quarantine.

On May 6, he dropped by a Vinmart convenience store in Khac Niem Ward, making contact with a cashier there, before returning home.

He first tested positive for the coronavirus on May 7, and after testing positive two more times for confirmation, he has been transferred to a local field hospital for treatment.

Local authorities have locked down a Canon dormitory with 1,200 workers in Que Vo District.Around 2,000 samples for Covid-19 testing have been taken in Bac Ninh for contact tracing, revealing two aforementioned coronavirus cases.

At South Korean Samsung Electronics Vietnam in the province's Yen Phong District, two coronavirus cases have been detected.

One of them, whose husband works at a local coronavirus hotspot in Bac Ninh, has not worked at the firm since April 29, so the risk of infection to other workers is low, health officials said.

The second case, a fellow worker, visited their parents at the same coronavirus hotspot from May 1 to May 2, but also has not come to work since April 26. Over 1,100 workers deemed to have made contact with coronavirus cases have been tested. None have returned positive so far.

At Taiwanese health and fitness firm Johnson Health Vietnam in the same province, around 2,800 samples have been taken for Covid-19 testing after a worker at the firm's packaging and assembling division was confirmed a Covid-19 case, tagged as "patient 3351" also on Monday. The firm has over 1,100 workers.

Bac Ninh, where several large-scale factories with thousands of workers are located, has recorded 124 coronavirus cases since May 5. The province has collected around 49,000 samples for coronavirus tests.

Vietnam is experiencing its toughest Covid-19 wave yet, which has seen 581 community transmission cases in 26 cities and provinces since April 27.

Thuy An