WUHAN • A 20-year-old Chinese woman from Wuhan, the epicentre of the coronavirus outbreak, travelled 675km north to Anyang where she infected five relatives, without ever showing signs of infection, Chinese scientists reported on Friday, offering new evidence that the virus can be spread asymptomatically.
Their study, published in the Journal Of The American Medical Association, offered clues on how the coronavirus spreads and suggested why it may be difficult to stop.
"Scientists have been asking if you can have this infection and not be ill. The answer is, apparently, 'yes'," said Dr William Schaffner, an infectious disease expert at Vanderbilt University Medical Centre who was not involved in the study.
China has reported over 76,000 coronavirus cases, including 2,345 deaths, and the disease has already spread to over 30 countries and territories outside mainland China.
Researchers have reported sporadic accounts of individuals without symptoms spreading the virus.
What is different in the study is that it offers a natural laboratory experiment of sorts, Dr Schaffner said. "You had this patient from Wuhan where the virus is, travelling to where the virus wasn't. She remained asymptomatic and infected a bunch of family members, and you had a group of physicians who immediately seized on the moment and tested everyone."
According to the report by Dr Wang Meiyun of the People's Hospital of Zhengzhou University and her colleagues, the woman travelled from Wuhan to Anyang on Jan 10 and visited her relatives.
When they started getting sick, doctors isolated the woman and tested her for the coronavirus. Initially, she tested negative, but a follow-up test was positive.
All five of her relatives developed Covid-19 pneumonia, but as of Feb 11, the woman still had no symptoms, her chest CT scan remained normal and she had no fever, or stomach or respiratory symptoms.
Scientists in the study said that if the findings are replicated, "the prevention of Covid-19 infection could prove challenging".
Dr Schaffner said the key questions are how often such transmission occurs and when during the asymptomatic period a person would test positive for the virus.