At least three-quarters of people who have had COVID-19 have at least one ongoing symptom six months later, a new study has revealed.

According to the findings, fatigue and muscle weakness are the most common symptoms to persist.

Chinese researchers looked at over 1,700 patients who were first diagnosed between January and May in Wuhan in China, where the virus was first reported. They were followed up in June and September.

The study found that 76% of COVID-19 patients had at least one symptom six months after the initial onset of the illness.

The most common symptoms found six months later were fatigue or muscle weakness (63% of all patients). This was followed by sleep difficulties (26%) and anxiety or depression (23%).

Those patients who had been severely ill with COVID were also more likely to have impaired lung function and abnormalities detected in chest imaging six months later.

Meanwhile, the study also found lower antibodies six months later in 94 of the patients, suggesting that they could be re-infected with the virus. Antibodies were found to be 52% lower than they were at the height of infection.

However, the researchers acknowledged that the number of people assessed for antibodies was low and they called for further work in this area.

"Because COVID-19 is such a new disease, we are only beginning to understand some of its long-term effects on patients' health. Our analysis indicates that most patients continue to live with at least some of the effects of the virus after leaving hospital, and highlights a need for post-discharge care, particularly for those who experience severe infections," commented Prof Bin Cao of the National Center for Respiratory Medicine in the China-Japan Friendship Hospital, Beijing.

The patients who were studied had a median age of 57. All were questioned face-to-face and they also underwent medical examinations, including physical examinations and a six-minute walking test to examine their endurance levels. Those who had experience severe disease performed worse on this six-minute test.

"Our work underscores the importance of conducting longer follow-up studies in larger populations in order to understand the full spectrum of effects that COVID-19 can have on people," Prof Cao said.

Details of these findings are published in the medical journal, The Lancet.