China has angrily rejected findings by scientists at Harvard University that coronavirus started circulating in the city of Wuhan at the end of last summer — months earlier than Chinese authorities have admitted.
The researchers from Harvard and Boston universities came to that conclusion after analysing satellite images of hospital car parks in Wuhan, the centre of the coronavirus outbreak, and queries on China’s Baidu search engine about disease symptoms such as a cough and diarrhoea.
“We observe an upward trend in hospital traffic and search volume beginning in late summer and early fall 2019,” the scientists wrote in a paper released online but not peer-reviewed.
Hua Chunying, a Chinese foreign ministry spokeswoman, dismissed the findings when she was asked about them at a daily press briefing on Tuesday. “To derive these conclusions from phenomena such as road vehicle traffic . . . is extremely preposterous,” she added.
The Harvard scientists extracted data for Wuhan hospital parking volume between January 2018 and April 2020 and found a steep increase in traffic that began in August 2019 and peaked in December. Searches for cough and diarrhoea from Baidu users in Wuhan rose steeply over the same period.
“This finding lines up with the recent recognition that gastrointestinal symptoms are a unique feature of Covid-19 disease and may be the chief complaint of a significant proportion of presenting patients,” the researchers said.
The conventional scientific view is that the virus originated in bats and moved from a still unidentified intermediate animal host into humans in Wuhan in November or early December, possibly via the city’s live animal market.
This is supported by genetic analysis of the virus, which suggests that there would have been more mutations by the time the disease was recognised later in December if it had already been circulating for three or four months.
However, there have been unconfirmed reports of Covid-19 cases outside China at the end of 2019. The Harvard team said its findings “corroborate the hypothesis that the virus emerged naturally in southern China and was potentially already circulating at the time of the Wuhan cluster”.
Commenting on the study, Paul Digard, professor of virology at the University of Edinburgh, said: “Using search engine data and satellite imagery of hospital traffic to detect disease outbreaks is an interesting idea with some validity. However, it is important to remember that the data are only correlative and as the authors admit cannot identify the cause of the uptick.
“It would have been interesting (and possibly much more convincing) to have seen control analyses of other Chinese cities outside of the Hubei region.”