The novel coronavirus might have been spreading in China as early as August 2019, according to Harvard Medical School research based on satellite images of hospital travel patterns and search engine data.
The research used high-resolution satellite imagery of hospital parking lots in Wuhan – where the disease emerged in late 2019 in the first known large outbreak – and data for symptom-related queries on search engines for things such as "cough" and "diarrhoea".
“The global COVID-19 pandemic was originally linked to a zoonotic spillover event in Wuhan’s Huanan Seafood Market in November or December of 2019. However, recent evidence suggests that the virus may have already been circulating at the time of the outbreak,” the research paper says.
The researchers observed an upward trend in hospital traffic and search volume beginning in as early as late August, into September and October.
“Increased hospital traffic and symptom search data in Wuhan preceded the documented start of the SARS-CoV-2 pandemic in December 2019,” the Harvard research asserts.
"While we cannot confirm if the increased volume was directly related to the new virus, our evidence supports other recent work showing that emergence happened before identification at the Huanan Seafood market."
The research was carried out with RS Metrics, an intelligence-analysis firm that analyses satellite imagery, and shared online.
“If you look at all of the images, observations we've ever had of all of these locations since 2018, almost all of the highest car counts are all in the September through December 2019 time frame,” the president of RS Metrics, Tom Diamond, told ABC News in the US.
The paper showed a steep increase in hospital parking lot occupancy as early as August 2019.
"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," the Harvard researchers wrote.
The online search activity also points to a potentially earlier emergence of COVID-19 than currently thought, the paper argues.
“In August, we identify a unique increase in searches for diarrhoea which was neither seen in previous flu seasons or mirrored in the cough search data,” researchers said.
“While queries of the respiratory symptom ‘cough’ show seasonal fluctuations coinciding with yearly influenza seasons, ‘diarrhea’ is a more COVID-19-specific symptom and only shows an association with the current epidemic.
“The increase of both signals precede the documented start of the COVID-19 pandemic in December.”
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