New research on the Wuhan coronavirus has found the virus may be present in the lungs of individuals with no obvious symptoms, making strict quarantine and contact-tracing regimes crucial to preventing the number of cases from reaching the scale of the 2003 Sars outbreak.

Without close surveillance, these patients – described by researchers as “cryptic cases of walking pneumonia” – could prove to be yet another factor in the dangerous trajectory of the Wuhan virus, with the number of infections and countries affected rising rapidly.

The findings were reported in Friday’s edition of The Lancet medical journal by a team of doctors which included top Hong Kong infectious diseases expert Professor Yuen Kwok-yung, and was based on their study of a family of seven admitted to the University of Hong Kong-Shenzhen Hospital between January 10-15.

Six members of the family were later diagnosed with the coronavirus – known as 2019-nCoV – which is causing increasing alarm around the world, with no clues on how it spreads. Of the six family members infected with the virus, a 10-year-old boy initially showed no outward symptoms but a CAT scan of his lungs revealed irregularities called ground-glass pneumonic changes.

“As shown in this study, it is still crucial to isolate patients and trace and quarantine contacts as early as possible because asymptomatic infection appears possible,” the report said.

Six members of the family travelled to Wuhan from Shenzhen between December 29 and January 4, according to the doctors, and the boy with asymptomatic infection – dubbed Patient 5 in the study – was one of two children in the group.

The report said the CAT scan of the boy’s lungs was done “on the insistence of the nervous parents”, despite his lack of outward symptoms. The report also noted that two other family members who were later diagnosed with the Wuhan coronavirus were afebrile – or not feverish – when they first presented at the hospital.



The report compared this confirmed instance of asymptomatic infection with the 2003 outbreak of severe acute respiratory syndrome (Sars) in 2003.

While asymptomatic patients with Sars had been “uncommon”, a retrospective study by the authors of a minor outbreak of the illness in Guangzhou in 2004 – following the reopening of a wildlife market in the southern Chinese city – showed there had been instances of symptomatic spreading, the report said.

“These cryptic cases of walking pneumonia might serve as a possible source to propagate the outbreak,” the report said. “Further studies on the epidemiological significance of these asymptomatic cases are warranted.”

The researchers also touched on the connection between the coronavirus and wild animals – the link between the virus and wild animals sold at a seafood market in Wuhan was confirmed on Wednesday by Gao Fu, director general of China’s Centre for Disease Control and Prevention.

The family that was the subject of the study “had no history of contact with animals, visits to markets including the Huanan seafood wholesale market in Wuhan, or eating game meat in restaurants,” the researchers said.



The report said that, based on the lessons learned from the Sars outbreak – which also originated from wild animals in its first phase – “all game meat trades should be optimally regulated to terminate this portal of transmission”.

The researchers offered some room for optimism, noting that “unlike the 2003 Sars outbreak, the improved surveillance network and laboratory capability of China was able to recognise this outbreak within a few weeks and announced the virus genome sequences that would allow the development of rapid diagnostic tests and efficient epidemiological control.”

Data from a separate study of 41 people diagnosed with the coronavirus and admitted to a Wuhan hospital showed most those infected (30 out of 41) were men and 32 per cent, or 13 of them, had underlying diseases such as hypertension or diabetes. The median age of those infected was 49 and 27 of the group had been exposed to the Huanan wet market.

The study, by mainland Chinese doctors, was also published in The Lancet on Friday.

More than 1,000 people have been infected and more than 40 people have been killed by the virus so far. All the fatalities and a vast majority of the infections have occurred in China.

Apart from mainland China, infections have been thus far been confirmed in Malaysia, Australia, France, South Korea, Singapore, Nepal, Thailand, Hong Kong, Vietnam, Taiwan and the United States.