However, an analysis of hospital traffic and search engine data in Wuhan indicates that there was early activity of the disease in the fall of 2019, according to HMS researchers.
In a study published on Harvard University’s DASH server on Monday, analysts used satellite images of the parking lots of six hospitals in Wuhan to calculate the number of vehicles and estimate trends in hospital occupancy. The number of vehicles was compared to trends seen in other influenza-like illness outbreaks.
The research paper – which is not yet peer reviewed – also analyzed data from Chinese search engine Baidu to determine changes in searches for the terms “cough” and “diarrhea” between April 2017 and May 2020.
He found that between 2018 and 2020 there was a general upward trend in hospital occupancy – but there was a sharp increase in occupancy from August 2019, which peaked in December 2019.
Five of the six hospitals included in the analysis showed their highest daily occupancy rates between September and October 2019, according to the researchers, which coincided with high levels of Baidu search queries for the terms “diarrhea” and ” cough ”.
Search volumes for the two terms rose dramatically in the city about three weeks before its peak in Covid-19 confirmed cases in early 2020, the study found.
“The increase in hospital traffic and symptom-finding data in Wuhan preceded the documented start of the pandemic in December 2019,” said the study authors. “Although we cannot confirm whether the increase in volume was directly related to the new virus, our evidence supports other recent work showing that the emergence occurred before the identification on the seafood market of Huanan. “
The report authors argued that their results supported theories that Covid-19 was already circulating before the Wuhan epidemic was first documented, adding that the virus could even spread internationally before Chinese authorities did not detect it at the end of 2019.
“In August, we identify a unique increase in the search for diarrhea that has neither been observed in previous influenza seasons nor reflected in the cough research data,” said the research team.
The United States Centers for Disease Control and Prevention (CDC) lists coughs and diarrhea as potential symptoms of Covid-19. The HMS research team has described gastrointestinal symptoms as a “unique feature” of the virus and which could be the main complaint for a number of symptomatic patients.
“This increase in the search for symptoms is then followed by an increase in traffic in the car parks of hospitals in October and November, as well as an increase in the search for coughs,” added the authors of the report. “Although we cannot conclude as to the reason for this increase, we hypothesize that wide community transmission may have led to more acute cases requiring medical attention, resulting in higher viral load and more severe symptoms . ”
Researchers noted that there had been some limitations to the use of satellite and Baidu search data, such as reduced visibility in bad weather, data acquisition from Chinese satellite companies, and ignorance of the intention of individual web searches.
China has faced criticism over its initial management of the epidemic, which included accusations that it had hidden critical information from WHO and delayed notification of the new coronavirus strain to the organization.
In April, authorities in Wuhan revised the death toll in the city of Covid-19 by 50% following a “citywide investigation”.
Although Chinese leader Xi Jinping has argued that the country has acted transparently throughout the crisis, China is resisting compliance with a WHO investigation into the global management of the pandemic.
The Chinese ambassador to the UK told Sky News last month that China would authorize an investigation into the epidemic – “but not now.”