A new study conducted by researchers at the University of Texas at Austin has estimated that there were thousands of undetected early cases of novel Coronavirus at the beginning of 2020. As per the findings, the COVID-19 was far more widespread in Wuhan, China, Washington, and Seattle in the U.S., weeks before lockdown measures were imposed in these cities.
The researchers also concluded that the first case of SARS-CoV-2 in Seattle may have arrived as far back as 2019 Christmas or New Year's Day. In the study, published in The Lancet's open-access journal EClinicalMedicine, researchers noted that in the U.S., about a third of the estimated undiagnosed cases were among children.
The team of researchers, led by Prof. Lauren Ancel Meyers extrapolated the extent of the novel Coronavirus epidemic in Wuhan and Seattle based on retested throat swabs taken from the COVID-19 patients, suffering from influenza-like disease during January in Wuhan as well as during February and March in Seattle. After analyzing these samples, they found that most of the swab tests turned out to be flu, while some came out positive for Coronavirus.
Meyers said that before "we realized that Covid-19 was spreading," the data suggested that there was at least one case of SARS-CoV-2 for every two cases of flu. "Since we knew how widespread flu was at that time, we could reasonably determine the prevalence of Covid-19," she added.
Wuhan went into lockdown on January 22, there were 422 COVID-19 cases. But the team of researched said extrapolating the throat-swab data from the Hubei city using a new epidemiological model revealed that there could have been over 12,000 undetected symptomatic cases of Coronavirus.
Later, in March when the schools in Seattle were closed, the researchers estimated that over 9,000 people with flu-like symptoms had the Covid-19 disease. This means about a third of that total were children.
As per the university, this data does not indicate that health authorities were aware of these infections. But it means that these cases may have gone undetected at the early start of the Coronavirus pandemic.
According to Zhanwei Du, a post-doctoral researcher in Meyers' lab and first author on the new study, given that Coronavirus appears to be overwhelmingly mild in children, the high estimate for symptomatic pediatric cases in Seattle has indicated that there may have been thousands more COVID-19 mild cases at the time.
Understanding of Coronavirus Spread
As of now, many studies have revealed that almost half of SARS-CoV-2 cases are found to be asymptomatic. This has led the researchers to the understanding that there may have been thousands more infected people in Hubei's Wuhan, where the COVID-19 first emerged, and in Seattle before stricter measures like lockdown were implemented.
Meyers said, "We can go back and piece together the history of this pandemic using a combination of investigative techniques and modeling," that would help the researchers to understand how the Coronavirus spread so quickly around the world and will also provide an insight into "what we may see in the coming weeks and months."
The team of researchers led by Meyers used the early travel data and estimated how far the novel Coronavirus had spread. They also came to the conclusion that there were as many as 12,000 COVID-19 cases in Wuhan before the lockdown imposed.