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Explained: Harvard study indicates Covid-19 may have been circulating in Wuhan since last August

The authors of the study say that they observed an upward trend in hospital traffic and search volume for disease-related terms beginning in late summer and early fall of 2019, implying that the virus may have already been circulating before the identification of the Huanan market cluster in Wuhan late November, early December.

By: Explained Desk | Updated: June 19, 2020 10:02:09 pm
covid, coronavirus, china covi-19, sars-covid-2 China has maintained that there was no delay or cover-up in the Chinese government’s response to the outbreak of the disease and has rebutted all other accusations suggesting the virus may have originated from the lab, saying that it’s a “smear” campaign.

A new study carried out by researchers from the Harvard Medical School, Boston University of Public Health and Boston children’s hospital used satellite imagery of parking lots and disease-related search engine queries to investigate the possibility that coronavirus may have been circulating in Wuhan since August last year.

What does the study say?

The authors of the study say that they observed an upward trend in hospital traffic and search volume for disease-related terms beginning in late summer and early fall of 2019, implying that the virus may have already been circulating before the identification of the Huanan market cluster in Wuhan late November, early December.

“This hypothesis is supported by emerging epidemiologic and phylogenetic evidence indicating that the virus emerged in southern China and may have already spread internationally, and adapted for efficient human transmission by the time it was detected in late December,” the study says.

Significantly, the study say that while queries for the respiratory symptom “cough” show seasonal fluctuations that coincide with yearly influenza seasons, the search for the term “diarrhea”, which is a more COVID-19 specific symptom showed an association with the current epidemic only.

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For the study, researchers collected over 111 satellite images of Wuhan from January 9, 2018 to April 30, 2020 resulting in 140 successful daily extractions of parking lot volume from hospitals. As per their analysis, between 2018 and 2020 there was a general upward trend of increased hospital occupancy and a “steep increase” in volume starting August 2019. Further, while individual hospitals have days of high relative volume in both Fall and Winter 2019, between September and October 2019, five of the six hospitals show their highest relative daily volume, which coincides with elevated search queries for the term “diarrhea” and “cough”.

Searches for “diarrhea” showed elevated traffic starting in late 2019, “cough” shows yearly peaks that coincide with the influenza season. Both the search terms show a large increase approximately three weeks preceding the large spike in confirmed COVID-19 cases in early 2020. The researchers observed a “large decrease” in hospital volume and search query data following the public health lockdown of Wuhan on January 23, 2020.

So what does this mean?

Essentially, the researchers are saying that while it cannot be confirmed if the increase in the volume of hospital traffic and symptom search data in Wuhan was directly related to the coronavirus, they say that there is some evidence to believe that the disease might have been spreading before its identification at the Huanan seafood market.

“In August, we identify a unique increase in searches for diarrhea which was neither seen in previous flu seasons or mirrored in the cough search data. While surprising, this finding lines up with the recent recognition that gastrointestinal (GI) symptoms are a unique feature of COVID19 disease and may be the chief complaint of a significant proportion of presenting patients,” the study says. The authors have cited a study carried out by the Wuhan Union Hospital and Wuhan Tongji Medical University, which says that while respiratory symptoms are common indicators of COVID-19, a “potentially large” segment of patients with digestive symptoms, such as diarrhea play an important role in community transmission.

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It is also possible that the initial rise in GI symptoms may have been ignored as an early signal of COVID-19 since the surveillance systems were looking for a respiratory pathogen, that are generally associated with symptoms such as fever, sore throat and cough.

What are some theories about the origins of coronavirus?

Over the last month, conversations about the origins of the virus have picked up pace. Three weeks ago, China and the WHO agreed to allow an independent international investigation into the origins of the coronavirus. In April, US President Donald Trump called the WHO’s response to the pandemic, “Chinacentric” and has repeatedly blamed the body for supporting China in their efforts to under-represent the severity of the outbreak. Trump and Secretary of State Mike Pompeo have also claimed that the virus originated from the Wuhan Institute of Virology in Hubei province.

China, on the other hand, has maintained that there was no delay or cover-up in the Chinese government’s response to the outbreak of the disease and has rebutted all other accusations suggesting the virus may have originated from the lab, saying that it’s a “smear” campaign. In late April, the head of the virology lab told Reuters there is no basis to claims that suggest the virus originated in the lab, adding that there still are no conclusive answers as to where the disease started.

A press release issued by the State Council Information Office of the People’s Republic of China on Monday said that, “China timely notified the international community of virus data and information about the epidemic, and made significant contributions to the global prevention and control…”. Significantly, a June 4 Associated Press report stated that China delayed sharing the virus’ genomic sequence.

China reported a cluster of cases of pneumonia in Wuhan to the WHO on December 31, 2019 and on March 11, the body characterised the disease outbreak as a pandemic. The scientific consensus is dominated by the view that the virus evolved naturally. WHO says on its website that the possible animal source of COVID-19 has not yet been confirmed. There is also a theory that the most trafficked mammals in the world, pangolins, maybe an intermediate host for transmission of the virus between bats and humans, however, research on this is still emerging.

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