There has been criticism from a U.S. study suggesting that coronavirus may have been present in the Chinese city of Wuhan as early as August last year.
The Harvard University study, which came to extensive publicity when it was published earlier this month, was rejected by China and its methodology was challenged by independent scientists.
What does the research say?
The research, which has not been peer-reviewed, is based on satellite imagery of circulation movements around Wuhan hospitals and tracking online research for specific medical symptoms.
He said there had been a significant increase in the number of vehicles parked in front of six hospitals in the city from late August to December 1, 2019.
This coincided, according to the Harvard report, with an increase in research into possible coronavirus symptoms such as “cough” and “diarrhea.”
This would be an important finding as the first case reported in Wuhan did not take place until early December.
Academics write: “While we cannot confirm whether the increase in volume was directly related to the new virus, our evidence supports other recent work showing that emergence occurred prior to identification in the Huanan seafood market.”
The Harvard study gained a lot of ground in the media, with President Trump, who was very critical of the response to China’s pandemic, tweeting a Fox News article highlighting the researchers’ findings. The tweet has been viewed more than three million times.
So, is their evidence valid?
The study claims that there has been an increase in online queries about coronavirus symptoms, particularly “diarrhea,” on the popular Chinese search engine Baidu.
However, Baidu officials disputed their findings, saying that there was in fact a decrease in the search for “diarrhea” during this period.
So what’s going on?
The term used in the Harvard University article actually translates into “diarrhea symptom” in Chinese.
We checked this on Baidu’s tool that allows users to analyze the popularity of search queries, such as Google Trends.
The search term “diarrhea symptom” shows an increase in queries from August 2019.
However, we also used the term “diarrhea,” a more common research term in Wuhan, and it actually showed a decrease from August 2019 until the beginning of the epidemic.
A lead author of the Harvard journal, Benjamin Rader, told the BBC that “the research term we chose for” diarrhea “was chosen because it best matched confirmed cases of Covid-19 and was suggested as a coronavirus-like research term.”
We also examined the popularity of research on “fever” and “difficulty breathing,” two other common symptoms of coronavirus.
Searches for “fever” increased slightly after August at a rate similar to “cough,” and demands for “difficulty breathing” decreased over the same period.
Questions were also asked about the study using diarrhea as an indicator of the disease.
A large-scale British study of nearly 17,000 coronavirus patients found that diarrhea was the seventh most common symptom, well below the top three: cough, fever and shortness of breath.
What about the number of cars?
In all six hospitals, the Harvard study reported an increase in the number of cars in hospital parking lots from August to December 2019.
However, we found serious flaws in their analysis.
The report indicates that images with tree cover and building shadows have been excluded to avoid over or under-counting vehicles.
However, satellite images released to the media show large areas of hospital car parks blocked by tall buildings, which means that it is not possible to accurately estimate the number of cars present.
In the tweet below, we annotated with white boxes the areas obscured by the tall buildings.
There is also an underground car park at Tianyou Hospital, which is visible on the Baidu Street view function, but only the entrance is visible on satellite imagery – not cars under the ground.
One of the study’s authors, Benjamin Rader, said, “We certainly cannot take underground parking into account at any time of the study and this is one of the limitations of this type of research.”
There are also concerns about the choice of hospitals for the study.
The Hubei Women’s and Children’s Hospital is one of the sites included, but children rarely need hospital treatment for coronavirus. In response, the authors state that their results would still show an increase in the overall use of parking even if the hospital were to be excluded from the survey.
The researchers could also have compared their data with hospitals in other Chinese cities, to see if the increase in traffic and research queries was specific to Wuhan, where the outbreak first appeared.
Without this comparison, in addition to the questions we asked about online research of medical symptoms, the evidence that Wuhan residents were receiving coronavirus treatment from August last year remains highly questionable.
However, there is still a lot we don’t know about the early spread of the virus in Wuhan.
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