Researchers at the Chinese University of Hong Kong (CUHK) on Tuesday called on recovered coronavirus patients to take part in the SAR's first citywide study on long Covid, which is hoped will provide a better understanding of the condition and help frame future healthcare policies.

The team is hoping to gather at least 10,000 responses for its online survey and said it welcomes recovered patients of all ages.

Participants can also scan a QR code on posters at outpatient clinics under the Hospital Authority to access the questionnaire.

People with long Covid are those who have recovered but still have persistent symptoms, such as fatigue or poor memory, four weeks after their initial infections.

A study by the university's faculty of medicine last year showed that 76 percent of people who caught Covid still experienced at least one symptom six months after their recovery.

Based on the calculation that around 1.27 million in Hong Kong have been infected with the coronavirus, the research team estimates that over 900,000 people have long Covid.

In a separate study, researchers surveyed 554 recovered Covid patients and found that almost 70 percent of them reported still having moderate to severe symptoms.

Professor Ng Siew-chien of the university's department of medicine and therapeutics, who's also the director of the Microbiota-I Center, said there is a need for a large-scale study to get a better grasp of the situation.

"This survey will be very important in Hong Kong for us to understand the percentage of people who are severely affected, that may, for example, affect the work productivity," she said.

"We don't really know enough about what causes long Covid at the moment. There's also no drug or treatment for long Covid at the moment. These people are going to be very much affected by persistent symptoms of severe and chronic fatigue, or mood disturbances, or poor sleep."

Ng said long Covid can affect multiple systems and organs in the body and one-stop, multidisciplinary facilities should be set up to treat patients.