HANOI — A specially converted Vietnam Airlines passenger plane equipped with ventilators and state doctors returned from Equatorial Guinea to Hanoi on Wednesday carrying 140 Vietnamese workers infected with COVID-19.

The plane, which left on Monday night for 27-hour, 21,000-kilometer round trip to the town of Bata in the West African country, arrived in the capital Hanoi, where infected patients were taken to a nearby hospital for treatment.

“We are all prepared,” Pham Ngoc Thach, director of the National Hospital of Tropical Diseases campus just outside Hanoi, told Reuters.

“One hundred ventilators, medicine and other equipment for testing and treatment as well as some 500 rooms have been set aside for the passengers.”

Equatorial Guinea has registered more than 3,000 cases of COVID-19 and 51 deaths, numbers that relative to its population of 1.2 million make it one of the African countries considered by the World Health Organization as “severely affected” by the pandemic.

Vietnam, virus-free for months, was bracing for a wave of locally transmitted COVID-19 infections on Wednesday after new cases were discovered in Hanoi, Ho Chi Minh City and the Central Highlands, all linked to a recent outbreak in Danang.

Of the 220 people on the flight from Equatorial Guinea, 140 were infected with the virus, state media said. At least a dozen were critically ill, said Thach, in what he described as an “unprecedented” large intake of patients for his hospital.

State media said the rescue effort was organized after the stranded workers, who had been working on a hydropower project, sent a letter to the Vietnam embassy in Angola, 1,200 km away, asking for help.

In a statement, Vietnam Airlines said it was only the second time one of its planes had flown to Africa. The first was on June 18, when it repatriated 309 Vietnamese workers from Angola.