Tuyen and his wife, who live in Ho Chi Minh City's District 1, are still coughing and feel ringing in their ears two weeks after they recovered from Covid-19. Their health has never been the same since they contracted the disease, the couple said.

Last month, the family of four were found to be infected after developing typical symptoms like coughing, fever, headache, fatigue and losing their sense of smell and taste. The entire family was quarantined in a centralized facility, where they fortunately recovered with no severe symptoms.

While the two daughters, one in secondary school and the other in university, have made full recoveries, their parents do not feel the same. Their bodies have seemingly weakened, even after the virus has left the system.

Tuyen's wife, 43, still coughs and feels tired. Sometimes she experiences severe headaches and chest pain. Her sense of smell has returned, but not to how it was before she contracted Covid-19.

"Some smells, which she had no trouble getting even 5-10 m away, are now impossible to get unless she goes real close," said Tuyen.

Tuyen is the only one in the family to have received a Covid-19 vaccine shot, yet "long Covid" still got to him. Days after his supposed recovery from the disease, his ears were still ringing and he coughed after speaking for some time. While these symptoms have subsided over time, they have not gone away entirely. He has also experienced symptoms like difficulty urinating, Tuyen said.

"In general, most of the symptoms are the same as when I first got Covid-19," he said.

Tuyen's home is on the top floor of an apartment complex in District 1, where almost 30 residents got Covid-19 and have since recovered.

"Most of the people here feel that their organs have weakened after recovery, even though they did not experience severe Covid-19 symptoms," Tuyen said. People were coping by resting, exercising and eating well, he added.

Diep Thanh Nhan, a 30-year-old man living in Go Vap District, was treated at a Covid-19 Resuscitation Hospital for 17 days. Thirteen days after he was discharged, the symptoms have largely gone, but his health has not gone back to what it was.

"Earlier, I would only feel slightly tired after doing push-ups or pull-ups. But now, just walking to the second floor or walking around the house make me pant. My lung capacity is only 20-30 percent from what it used to be, I feel, and I have to practice to breathe again," he said.

Nhan said he used to do exercises and play a lot of sports, but feels it would take him around 3-6 months of rehabilitation to gradually recover.

Pham Van Tien, 28, was fully vaccinated before he tested positive for the novel coronavirus. The resident of Binh Thanh District only got mild symptoms and was discharged after spending 13 days in a field hospital. Having stayed at home for the past two weeks, Tien said the cough still persists.

"I was a mild case and it's been nearly a month since I contracted the disease, but I still feel fatigued and cough even now. My health is now only 80 percent of what it used to be," he said, adding that he was trying to exercise and eat well to recover.

Still a mystery

The Post Covid-19 Syndrome, otherwise known as Chronic Covid Syndrome or Long Covid, has been observed in several countries as the pandemic rages.

Scientists have still not grasped how the condition came to be, saying it remains one of the most mysterious aspects of the pandemic.

Maria Van Kerkhove, the WHO's Covid-19 technical lead, said last month that the organization was deeply concerned by the unknown numbers who may still be suffering with Long Covid.

"We don't know for how long these effects last and we're even working on a case definition to better understand and describe what this Post Covid syndrome is," the AFP quoted Kerkhove as saying.

Nguyen Hong Ha, deputy head of the Vietnam Association for Infectious Diseases, described Long Covid as a condition that affects the entire body. Patients are impacted throughout long Covid-19 treatment periods, causing declining bodily functions and organs, especially among those with severe symptoms, he said.

Lung damage caused by Covid-19 might leave scarring for example, which affects a patient's respiratory system and would take time to heal. Antibodies produced to fight the coronavirus might also inadvertently trigger auto-immune diseases, among others, he pointed out.

Janet Diaz, clinical care lead in the WHO's emergencies program who leads the organizations' Long Covid efforts, said there have been more than 200 reported symptoms, including chest pain, tingling and rashes, the AFP reported.

Diaz said some people seem to have had post-Covid conditions for three months, and others for up to six months.

"We are concerned there may be a small proportion that go on to nine months - and to longer than that."