Nearly half of COVID-19 patients discharged from one of the major hospitals in Wuhan, the provincial capital of China’s central Hubei province — where the coronavirus was first reported — experience persistent symptoms one year after recovery, according to data from the largest follow-up study of its kind.

More than 800 of the 1,300 recovered COVID-19 patients treated at Wuhan’s Jinyintan Hospital experienced at least one persistent symptom, such as fatigue, difficulties sleeping, or loss of hair, smell, or taste, the study published Thursday in British scientific journal The Lancet said. The proportion, while significant, is lower than the 68% of patients who had reported similar conditions six months after testing negative for the virus.

While millions of COVID-19 patients globally recover without developing any health issues, an unknown number continue to exhibit related symptoms weeks or months after they are declared virus-free, a condition now referred to as long COVID or post-COVID syndrome. However, the proportion of so-called long-haulers in Wuhan was much higher compared with some earlier international studies, which estimated around 10% to 30% of COVID-19 survivors suffer from persistent symptoms.

Some 20% of recovered patients in The Lancet study said they still experienced fatigue or muscle weakness one year after testing negative for COVID-19. Those ailments were reported as the most common lingering symptoms.

The study’s researchers noted that patients who were critically ill from COVID-19 were more likely to suffer from persistent symptoms and prolonged lung damage. Over a quarter of the patients studied also suffered from anxiety or depression a year after leaving the hospital, which “could be driven by a direct effect of virus infection,” the study said.

“Additionally, indirect effects including reduced social contact, loneliness, incomplete recovery of physical health, and loss of employment could affect psychiatric symptoms,” according to Thursday’s study.

Scientists are still unclear why some patients recover fully from the coronavirus that causes COVID-19, while others suffer various ongoing health conditions. However, similar long-term effects have also been observed in patients who recovered from severe acute respiratory syndrome (SARS) and West Nile fever.

An immunologist, who requested anonymity as he was not authorized to speak to the media, told Sixth Tone that some symptoms, such as fatigue and loss of smell could be due to neurological injuries resulting from low oxygen levels in the brain while the patients were sick.

“We also can’t rule out the possibility that psychological conditions might play a role in causing these symptoms,” he said. “The study highlights the need to pay attention to patients’ mental health even after they’ve recovered.”

Editor: Bibek Bhandari.

(Header image: A COVID-19 patient sits by his assigned bed at a temporary “shelter hospital” in Wuhan, Hubei province, March 9, 2020. People Visual)