COVID-19 spread is fueled by ‘stealth transmission’
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For the study, published Monday (March 16) in the journal Science, the researchers developed a computer model to simulate the spread of SARS-CoV-2, the virus that causes COVID-19, among 375 cities in China, including Wuhan, where the outbreak began. For the model, they combined data on reported infections with information on people’s movements (obtained from mobile phone data).
They estimated that, prior to the lockdown of Wuhan on Jan. 23, about 86% of all COVID-19 infections in China were undetected. In other words, for every confirmed case of COVID-19, there were six undetected cases, according to The Washington Post. These undetected cases were responsible for the majority of the disease spread prior to the lockdown, the researchers said.
The findings have implications for COVID-19 spread in the rest of the world, as many countries are behind on testing for the disease. The results suggest that the number of cases worldwide could be five to 10 times higher than what has been reported, meaning the true number of cases could be higher than 1.5 million, according to Quartz.
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“We know this is just the tip of the iceberg,” Shaman said at a press conference Monday (March 16), according to Quartz. “The question is how much of the iceberg is submerged. We can argue about the exact number, but if you’re not in a place where you’re “not proactively looking for people and testing, then the majority of infections will go undetected.”
After China implemented the lockdown on Wuhan, officials were able to detect the majority of cases, 65%, and reduce the spread of the disease.
The findings suggest “a radical increase in the identification and isolation of currently undocumented infections would be needed to fully control SARS-CoV-2,” the authors concluded.
Originally published on Live Science.