Coronavirus had probably already spread to thousands of people in Seattle before the city of Washington became the first known American case of COVID0-19, new research shows.
University of Texas (UT), Austin, scientists create a model to estimate how many people had coronavirus based on recently re-tested samples taken from hundreds of samples taken from children and adults suspected of influenza , which presented with similar symptoms of coronavirus.
Twenty-five of them – including many taken from children – were positive for the virus that causes COVID-19.
Based on their findings, the UT Austin team estimates that about 9,000 people were already infected in Seattle before Americans knew the virus was there.
Researchers at the University of Texas at Austin estimate that 9,000 people – including 3,000 children – may have had a Seattle coronavirus last winter, long before the city was shut down (pictured)
‘Even before we realized that COVID-19 was widespread, the data implied that there was at least one case of COVID-19 for every two cases of influenza,’ said lead study author Dr Lauren Ancel Meyers.
Like flu, when someone develops symptoms, they usually start with fever, cough and fatigue, which can potentially lead to shortness of breath.
However, COVID-19 is a distinct respiratory and a much more lethal one that attacks multiple systems of the body.
Of the 2,353 samples taken from children and adults in Seattle that other studies recently retested for coronavirus, 25 were positive for coronavirus.
Another 442 were positive for some strain of flu.
But those samples would probably only be responsible for the people who had symptoms.
And the combined evidence from other studies suggests that about half of people who are covid-positive never develop symptoms.
Scientists have also developed estimates that for every two cases of influenza, there is at least one case of COVID-19.
Based on this information and their preliminary research into how coronavirus spread through travel, scientists estimated that about 9,000 people in Seattle were likely to catch coronavirus in the weeks before the city was shut down on March 9th.
And about a third of those cases were in children.
Seattle was the first American coronavirus hotspot. Well, the outbreak is pretty much under control thanks in part to better testing – but thousands of cases have probably gone undiagnosed last winter (file)
‘Given that COVID-19 appears to be overwhelmingly mild in children, our high estimate for symptomatic pediatric cases in Seattle suggests that there could have been thousands more mild cases at the time,’ said the study’s first author, Zhanwei Du , a postdoctoral fellow in Dr. Meyers’ lab.
The team found a similar pattern when they ran their model on swabs from Wuhan, China, where coronavirus was first identified for the first time.
From a pool of 26 samples from people in Wuhan, four tested positive for SARS-CoV-2 and seven were positive for flu.
When Wuhan closed on January 22 – the first city in the world to do so – 422 cases were identified there.
But based on their model, the team estimates that at that time there were probably about 12,000 undetected cases of coronavirus in the Chinese city.
And those unidentified carriers – in both Seattle and Wuhan – quietly spread the virus, before officials issued any warning that they would need restrictions to control the spread.
Dr. Meyers notes that this pattern can now be repeated as restrictions to slow the spread of the coronavirus in many parts of the US and the world are lifted.
“We can combine the history of this pandemic with investigative techniques and modeling, and they will separate together,” she said.
“This helps us understand how the pandemic is spreading so rapidly around the world and provides insight into what we can see in the coming weeks and months.”
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