China had coronavirus in the fall according to satellite images and online searches. This is the latest finding of the Harvard Medical School (HMS).
Based on HMS' new study, Covid-19 may already be present in China as early as August 2019.
The coronavirus is believed to have started in a wildlife market in Wuhan, a city in China. This is where the first coronavirus case was reported to the World Health Organization in late December.
However, HMS found that there was early disease activity in the fall of 2019. The researchers conducted an analysis of hospital traffic and search engine data in Wuhan.
According to a study published on Harvard University’s DASH server, analysts examined satellite images of parking lots at six hospitals in Wuhan. This allowed them to compute vehicle counts and analyze hospital occupancy trends. The vehicle numbers were analyzed side by side with trends seen during other flu-like outbreaks.
Search volumes
Harvard's study has not yet been peer reviewed. The team looked into data from Chinese search engine Baidu to detect changes in searches for the terms “cough” and “diarrhea” between April 2017 and May 2020.
The results showed a general upward trend in hospital occupancy between 2018 and 2020. Moreover, there was a steep increase in occupancies from August 2019, which reached peak in December 2019.
The researchers found that five of the six hospitals in the analysis recorded their highest daily occupancies between September and October 2019. The pattern reflected the elevated levels of Baidu search queries for the words “diarrhea” and “cough.”
Moreover, there was a rise in the search volumes for both terms around three weeks before its increase of confirmed Covid-19 cases in early 2020.
“Increased hospital traffic and symptom search data in Wuhan preceded the documented start of the pandemic in December 2019,” the study’s authors said.
“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.”
According to the study's authors, HMS' findings mirrored speculations that Covid-19 was already spreading before the initial outbreak in Wuhan was documented. They believe that the virus may have even spread internationally before Chinese authorities spotted it in late 2019.
“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,” the research team said.
Potential symptoms
According to the US Centers for Disease Control and Prevention (CDC), both a cough and diarrhea are potential symptoms of Covid-19. The researchers described gastrointestinal symptoms as a “unique feature” of the virus. This could be a major complaint for many symptomatic patients.
“This symptom search increase is then followed by a rise in hospital parking lot traffic in October and November, as well as a rise in searches for cough,” the report’s authors added.
“While we cannot conclude the reason for this increase, we hypothesize that broad community transmission may have led to more acute cases requiring medical attention, resulting in higher viral loads and worse symptoms.”
