Hoa of Ung Hoa District on Thursday managed to buy two boxes of masks after queueing for over an hour. For each box of 5,000, she paid VND5 million ($216), double the price she paid two weeks ago.

"I was willing to pay the price since it could climb even higher in the coming days and there might be no stocks left," she said. She retails them at the Hapulico Medicine Market in Thanh Xuan District, where masks are among the top-selling items now.

The price of the N95 mask made by U.S. company 3M, which is said to have at least 95 percent filtration efficiency against certain non-oil based particles, has jumped almost five times from VND20,000 (86 cents) to VND90,000 ($3.88).

Pharmacies in the capital are struggling to source more masks.

Mai, a drugstore owner in Ha Dong District, said on Tuesday she did not have masks in stock. "I ordered 200 boxes [of 50 masks] on Thursday, but the manufacturer sent only 40."

She said she had never had so much difficulty buying masks and hand sanitizers as now since manufacturers are unable to keep pace with demand.

She sells only one box to a customer, explaining to them it is to make sure more people can protect themselves.

Pharmacies in Thanh Xuan District have no masks in stock and some ask customers to return the next day and try their luck.

Not surprisingly, prices have shot up. Mai, a woman who lives in Cau Giay District, said she was surprised to see a local pharmacy hike the price of masks 2.5 times within just a few days to VND100,000 ($4.32).

But she decided to buy anyway after the salespeople told her they would be out of stock within the day.

At Coop Mart, VinMart and Big C outlets, mask shelves were empty on Thursday, the first working day after the seven-day national holiday for Tet though there had a lot of stock just the day before.

"Each customer bought around three boxes [of 50 masks]," a salesperson at Coop Mart Ha Dong said. "We do not expect stocks to arrive until next week from Saigon."

Mask prices are erratic on e-commerce websites. On Lazada, for instance, one seller lists 3M masks at VND40,000 ($1.73) and another at VND27,000 ($1.17). Many have run out of stock.

The Ministry of Health confirmed Thursday that three Vietnamese have tested positive for the nCoV. One is being treated at the Thanh Hoa General Hospital in central Thanh Hoa Province and the others at the National Hospital of Tropical Diseases in Hanoi.

They were among eight people working for Japan’s Nihon Plast Company Limited and sent to work in Wuhan City, the epicenter of the epidemic, two months ago. They returned to Vietnam on a Southern China Airlines flight on January 17.

As of Thursday afternoon there were five confirmed cases of infection. Two Chinese nationals were confirmed on January 23 as Vietnam's first cases of nCoV infection, but one of them has since recovered.

The World Health Organization (WHO) on Friday declared a global health emergency as the death toll reached 213, all in China.