The 69-year-old British man, currently being treated at the National Hospital of Tropical Diseases in Hanoi, had several underlying conditions, including diabetes and hypertension, and also became feverish Sunday afternoon, the Health Ministry said.

He was moved to the hospital’s Intensive Care Unit (ICU) Monday.

A team of quick-response doctors from the Bach Mai Hospital were sent to the National Hospital of Tropical Diseases Sunday afternoon to help treat the man. Besides using a ventilator, the patient also had his blood directly filtered, the ministry said.

A Vietnamese woman in Hanoi is another Covid-19 patient whose condition has worsened, requiring a ventilator and blood filtration.

The 64-year-old woman, also staying at the National Hospital of Tropical Diseases, was suffering from vestibular disorder as an underlying condition. She experienced breathing difficulties that escalated into respiratory failure Sunday night. Doctors have inserted a breathing tube and used a ventilator, among other measures, to help stabilize her. She has been transfered to the ICU and her pulse, blood pressure and blood oxygen levels are currently stable.

The British man was among several confirmed infections on Vietnam Airlines flight VN54 that flew from London and landed in Hanoi on March 2. He was confirmed infected on March 8.

The Vietnamese woman was diagnosed on March 7. She is an aunt of 26-year-old Nguyen Hong Nhung, Vietnam's 17th and Hanoi's first Covid-19 patient who was on the same VN54 flight.

Vietnam has confirmed 57 Covid-19 infection cases so far, with 16 already discharged from hospitals. Among the active cases, 17 are foreigners.

At least two British and one Vietnamese patients have tested negative for the virus at least once. The two Brits are undergoing treatment at the Da Nang Hospital. They tested negative for the virus on March 10 after testing positive on March 8.

The 27-year-old Vietnamese patient, convalescing at the Ninh Binh General Hospital after coming back from South Korea's epidemic center Daegu, tested negative for the virus on March 15, a week after being diagnosed with the virus.

Pham Ngoc Thach, director of the National Hospital of Tropical Diseases, said elderly people, especially those with chronic conditions like diabetes, hypertension or cardiovascular diseases, may have more severe symptoms when infected with the Covid-19 virus compared to those with no underlying conditions. They also have a higher risk of transitioning to a quicker, more severe disease progression, which could result in respiratory failure, he added.

Globally, elderly people are the most represented among all Covid-19 patients, as well as having the highest fatality rates.

The Covid-19 outbreak has thus far spread to 157 countries and territories around the world, with the death toll climbing to over 6,500.