Researchers have found traces of the novel coronavirus in the stool of infected Hong Kong patients, regardless of their degree of illness. The finding raises the possibility of a test for asymptomatic people, according to the study released on Thursday.

A team at the Chinese University of Hong Kong (CUHK) detected the virus in the faecal samples of all 14 patients they tested who had been diagnosed with Covid-19, including three who no longer had traces of the virus in their mucus, saliva or nose.

File photo: GovHK.

The team analysed more than 300 specimens including sputum, nasopharyngeal swabs, deep throat saliva, blood, urine and stool. Sputum – coughed-up mucus – had the highest concentration of the coronavirus, with more than 300 times more than saliva. All urine samples, meanwhile, tested negative.

The findings highlighted the potential risk of environmental contamination by virus shedding in stool, the team said.

Chairman of the Department of Microbiology at CUHK Professor Francis Chan said the study had various public health implications: “First, [stool] may serve as an alternative screening tool in people without respiratory symptoms. Second, virus shedding in [the] stool may impose health hazard[s] to others. Caretakers and food handlers should be particularly vigilant about their hand hygiene.”

First detected in China’s Hubei province, Covid-19 has infected more than 182,400 people, leading to more than 7,100 deaths across 162 countries and territories.

Chairman of the Department of Microbiology at CUHK Professor Paul Chan (left), Dean of the Faculty of Medicine Professor Francis Chan (centre) and Chairman of the Department of Medicine and Therapeutics Professor David Hui. Photo: CUHK.

Chairman of the Department of Medicine and Therapeutics at CUHK Professor David Hui said that faecal matter could contaminate the environment, leading to virus transmission through mucosal surfaces such as the eyes or mouth.

“The public are reminded of filling enough water into U-shaped water traps connected to bathroom floor drains and to close the toilet lid when they flush. All these measures help reduce the risk of infection,” Hui added.

During the 2003 SARS outbreak in Hong Kong, more than 300 people at Amoy Gardens were infected with the deadly virus probably due to faulty plumbing, officials said.

The CUHK team said they will test 100 asymptomatic close contacts in quarantine centres around Hong Kong to determine whether stool tests can effectively detect Covid-19.

Jennifer Creery

Jennifer Creery is a Hong Kong-born British journalist, interested in minority rights and urban planning. She holds a BA in English at King's College London and has studied Mandarin at National Taiwan University.