A simple stool test can tell recovered Covid-19 patients their risks of suffering the effects of long Covid with 90 per cent accuracy, researchers at the Chinese University of Hong Kong (CUHK) have found. Professor Ng Siew Chien, associate director of the university’s Centre for Gut Microbiota Research, said new technology that analysed bacteria in the gut could predict recovered patients’ risks of suffering long-term after effects. Long covid, or post-Covid syndrome, refers to various symptoms such as fatigue, anxiety, poor memory, sleeping difficulties and hair loss that persist more than four weeks after patients recover from the virus. It can affect patients who had both mild or severe Covid-19 symptoms. Ng’s team was the first in the world to discover that long Covid patients have a distinct gut microorganism known as a microbiome, with an imbalance in the amount of different bacteria present. Most ignore vaccine pass rules in Hong Kong, asking: why bother? The imbalance may cause a shortage of “good” bacteria linked to the respiratory system, resulting in prolonged coughing and shortness of breath or an abundance of “bad” bacteria linked to fatigue, insomnia and loss of taste. Ng said it was easy for patients to test their long Covid, with results known in a fortnight. Patients provide a stool sample for the university’s laboratory to analyse. Two weeks later, they are told their test score, produced by an algorithm created from an analysis of more than 1,200 stool samples of healthy individuals, long Covid patients and those with other diseases. Patients are given a report on the state of microorganisms in their gut that can indicate their risk of developing long Covid. The team previously studied 106 coronavirus patients and found that three out of four developed at least one long Covid symptom six months after recovery, while a third had more than three. The stool test will be provided initially at CUHK Medical Centre, with details on the cost and when it will be available to be released soon. “We can help recovered patients who are unable to find out the causes of their lingering symptoms and see if they have long Covid by identifying the unique gut microbiome,” said Professor Francis Chan Ka-leung, the centre’s director. Chan said that by identifying the microorganism, the team could help restore any imbalance of the bacteria in the gut and reduce the patient’s risk of developing long Covid. In June 2020, the team developed a probiotic supplement called SIM01, to treat the imbalance in gut bacteria caused by Covid-19. It was tested on 36 infected patients who took the supplement for four weeks, with the outcomes compared with another group that was not given SIM01. The team found that 94 per cent of those who took the supplement did not show any long Covid symptoms over the following year. “About 76 per cent of those who did not take SIM01 developed long Covid, while only 6 per cent of those who took SIM01 had long Covid, so I think the prevention application is very promising,” she said. Why is Hong Kong’s Covid-19 death rate so high? Breaking down the fifth wave numbers SIM01 has been made into a supplement that is sold by GenieBiome, a CUHK biotechnology spin-off, with a box of 28 sachets costing HK$499 (US$64). Chan said other probiotic supplements might not be as effective in preventing long Covid as the unique microorganism in the gut of Covid-19 patients required a specific probiotic formula. To determine the effectiveness of SIM01 in treating long covid symptoms, the centre is recruiting 400 recovered patients for a four-year study. One group will take the supplement for six months, while another will be given vitamin C, and they will be monitored for the rest of the study period. Professor Ivan Hung Fan-ngai, an infectious diseases expert at the University of Hong Kong, said further studies were needed to examine the accuracy of the stool test and the effectiveness of SIM01. Commenting on the CUHK team’s work, he said: “They have not done a study with a few thousand test subjects to prove that those with a high risk score from the stool test actually display long Covid symptoms after 12 weeks or six months.” Hong Kong voluntary mass Covid-19 testing runs into early hurdles amid scepticism If the recovered patients in the study received antibiotics during their hospitalisation, he said, their gut bacteria diversity would be reduced and that might affect the findings. He said Queen Mary Hospital had followed up on more than 3,000 recovered Covid-19 patients and “fewer than 3 per cent have long Covid beyond 12 weeks”. Pointing out that most patients in Hong Kong’s massive fifth wave of Covid-19 infections had recovered on their own, he suggested that the researchers test their findings by recruiting several thousand patients who had mild to severe Covid symptoms and did not receive antibiotics.