The duo, a mother and daughter, visited Tu Du, the biggest obstetrics hospital in southern Vietnam, on April 20 as the daughter, 32-weeks pregnant, suffered implantation bleeding.

The daughter was subsequently hospitalized, in the care of her mother.

It was not until Tuesday that they were found to have returned from Cambodia, which has been in the grip of a Covid spread since late February.

The two later admitted they had traveled by boat across a river along the Vietnam-Cambodia border and broke into An Giang Province in the Mekong Delta.

"Both of them and 40 medics that have been in contact with them have been isolated and tested. All tests have returned negative once," Nguyen Tan Binh, director of the city's Health Department, said Wednesday.

Cambodia registered at least 650 new Covid-19 community cases Tuesday after reporting 508 on Monday and 580 on Sunday after the weekend had logged 1,196 cases.

As of Tuesday evening, Cambodia has recorded 11,063 cases, of which 10,513 are linked to the outrageous Feb. 20 community outbreak, Khmer Times reported.

HCMC has gone 75 days without a Covid-19 community transmission. Nationwide, it has been a month.

Given the complicated situation in Cambodia, more Vietnamese will try to get back home, even when they have to do it illegally, to escape the pandemic, said Binh.

Last week, three people illegally entered Vietnam from Cambodia, and traveled to various places around the country, but have been confirmed negative for the novel coronavirus. The trio had also visited HCMC before flying to the north.

City chairman Nguyen Thanh Phong said over the past month, authorities had detected 108 illegal entrants.

"But the actual figure could be much higher," said Phong.

Everyone entering Vietnam from abroad is quarantined for 14 days and tested at least twice.

Vietnam shares a 1,137-kilometer boundary with Cambodia in the Mekong Delta, near HCMC, and in the Central Highlands. The Kien Giang-Cambodia border stretches 56 kilometers (34.8 miles) in land and covers 62,000 square kilometers of sea area.

Major Nguyen Truong Phong, head of the Vinh Nguon border guard station in An Giang, said this week with many rivers and canals adjacent to localities in Cambodia, the province provides the perfect conditions for people to break into Vietnam.