Analysis of Satellite Imagery and Search Data Suggests the Coronavirus Outbreak May Have Started Earlier in 2019

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Currently in preprint, a study that analyzed traffic around hospitals using satellite imagery and Baidu search queries suggests that the coronavirus outbreak may have started earlier in China than in December of 2019. Researchers with Boston University, Boston Children’s Hospital, and Harvard Medical School used digital epidemiology methodologies and remote sensing to perform disease surveillance for indicators of when the novel coronavirus may have first been active in Wuhan, China. In particular, the researchers used two data streams, search engine queries and high resolution satellite imagery of hospital parking lots, to pinpoint when the earliest possible indicators of COVID-19 emerged.

High resolution satellite imagery of six hospitals in Wuhan and search engine traffic related to COVID-19 illness such as “cough” and “diarrhea” was collected. Researchers looked at satellite imagery between January 9, 2018 and April 30, 2020 to estimate hospital visits based on parking lot traffic. The rate of hospital visits was tracked alongside search volume for terms such as “diarrhea” since the presence of gastrointestinal (GI) symptoms are one of the unique symptoms of COVID-19 illness.

Researchers counted vehicles in hospital parking lots to estimate hospital visits between January 9, 2018  and April 30, 2020.  Source: Okanyene Nsoesie et al., 2020.
Researchers counted vehicles in hospital parking lots to estimate hospital visits between January 9, 2018 and April 30, 2020. Source: Nsoesie et al., 2020.

The researchers found “an upward trend in hospital traffic and search volume beginning in late Summer and early Fall 2019,” suggesting a fall emergence of COVID-19. The authors of the study caution that “[w]hile 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 authors point to “the recent uptick in hospital traffic and search engine query data in May coincides with recent reports of new case clusters in Wuhan” to support their suggestion that the COIVD-19 outbreak happened earlier than December of 2019.

The inferences from this study don’t definitely show when infections from this novel coronavirus actually began. This preprint study uses correlation analysis to draw its conclusions about the prevalence of novel coronavirus infections in Wuhan during the fall of 2019. As

The study

Nsoesie, Elaine Okanyene, Benjamin Rader, Yiyao L. Barnoon, Lauren Goodwin, and John S. Brownstein. Analysis of hospital traffic and search engine data in Wuhan China indicates early disease activity in the Fall of 2019 (2020). Retrieved from


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