Severe cases of Covid-19 can leave sufferers with fatigue, sleep difficulties and hair loss, lasting weeks or even months after patients test negative.
Researchers in Wuhan, China – where the outbreak arose – followed more than 1,700 patients to chart their recovery from the virus.
They found that around three quarters of them, 76 per cent, were still experiencing at least one symptom six months later.
The most common after effects were fatigue or muscle weakness, which was experienced by almost two thirds, or 63 per cent.
A quarter suffered from sleep difficulties, while one in five experienced hair loss.
Other enduring symptoms included a smell disorder among 11 per cent of patients, while 9 per cent felt palpitations and a similar number experienced joint pain.
Decreased appetite was reported by 8 per cent of patients; while 7 per cent said they had taste disorder and 6 per cent felt dizziness .
Researchers also found 5 per cent of patients were experiencing diarrhoea or vomiting, and a similar proportion felt chest pains.
Less than 5 per cent of people were still suffering from a sore throat or finding it difficult to swallow; a skin rash; muscle pain or a headache.
A low-grade fever was seen in fewer than one per cent of former sufferers.
"At six months after acute infection, Covid-19 survivors were mainly troubled with fatigue or muscle weakness, sleep difficulties, and anxiety or depression," said the researchers in the study published in medical journal The Lancet.
Days earlier, another study, this time from the UK, showed almost a third of patients who recover from the infection return to hospital with symptoms within five months. One in eight of them died.
The study, by researchers at the University of Leicester and the Office of National Statistics, followed 47,780 people who were discharged from hospital. Of those, 29.4 per cent were readmitted within 140 days and 12.3 per cent died.
The UK study was the largest to date following people who were discharged after being admitted with the virus.
People who go on to suffer lasting effects of the virus are said to be suffering from “long Covid”.
Because doctors do not know what causes the condition, they cannot say how long its effects will last.
The phenomenon is not limited to severe cases. Experts say even mild cases can make people sick for months.
Longevity of immunity
Recent research from the UK found beating Covid-19 provides protection of about 85 per cent, which is comparable to many vaccines.
“There are two things are important to understand, that still infections can occur, and immunity is not lifelong,” said Dr Sunil Kumar Garg, a specialist in critical care medicine at NMC Royal Hospital, Dubai Investment Park.
“It means once immunity wanes over the period of time, you are predisposed to infection as if you never had the infection.
“The good side of this is that if reinfection occurs, it is usually asymptomatic or mild state only.”
Experts said the best way for people to protect themselves is to wear a mask outside the home, practise social distancing, wash hands often and have the vaccine.