Coronavirus may have been present and spreading in Wuhan as early as August last year, according to a study that analysed satellite imagery of car parks outside major hospitals and search engine data.
The study, by researchers from Harvard Medical School, Boston University of Public Health and Boston children’s hospital, looked at images captured between January 2018 and April 2020 and found a “steep increase” in vehicle counts starting in August 2019 and peaking in December 2019. Between September and October, five of the six hospitals observed had their highest daily volume of cars in the period analysed.
China’s foreign ministry rejected the study, calling it “extremely absurd”.
According to the study, the increase in vehicle volume coincided with a rise in queries on the Chinese search engine Baidu for “cough” and “diarrhoea”, about three weeks before the confirmed rise in coronavirus cases in early 2020. The researchers noted that while queries for cough coincided with the influenza season, diarrhoea is a symptom specific to Covid-19.
The authors of the study, which is still under peer review, acknowledged that they could not confirm whether the increased vehicle volume was directly related to the new virus. Wuhan would have been entering influenza season; several doctors said that in December some schools had cancelled classes because of the flu.
Other limitations include the presence of tall buildings, trees and smog, which limited the number of high-resolution images that could be taken. There was also limited archival footage of Wuhan in previous years because of a “lack of commercial interest”.
The study said: “Our evidence supports other recent work showing that emergence happened before identification at the Huanan seafood market. These findings also corroborate the hypothesis that the virus emerged naturally in southern China and was potentially already circulating at the time of the Wuhan cluster.”