Younger covid-19 in the southern US USA 0:31

. – A new study suggests that up to 8.7 million Americans contracted coronaviruses in March, but more than 80% of them were never diagnosed.

A team of researchers reviewed the number of people who went to doctors or clinics with influenza-like illnesses who were never diagnosed as coronaviruses, influenza, or any of the other viruses that generally circulate in winter.

There was a giant spike in these cases in March, the researchers reported in the journal Science Translational Medicine.

“The findings support a scenario in which more than 8.7 million new SARS-CoV-2 infections appeared in the US. USA during March and estimate that over 80% of these cases remained unidentified as the outbreak spread rapidly, “wrote Justin Silverman of Penn State University, Alex Washburne of Montana State University, and colleagues at Cornell University and elsewhere.

Only 100,000 cases were officially reported during that time period, and the United States still reports only 2.3 million cases as of Monday. But there was a shortage of coronavirus test kits at the time.

The team used data from each state collected by the US Centers for Disease Control and Prevention. (CDC) for influenza-like illness. The CDC uses this data to track the annual seasonal flu epidemic. Ask doctors to report all cases of people who come for treatment for fever, cough, and other flu-caused symptoms.

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“We found a clear and abnormal increase in outpatients with influenza-like illness (ILI) during the covid-19 epidemic that correlated with the progression of the epidemic in multiple states in the United States,” Silverman and colleagues wrote.

“The increase in outpatients without influenza was much greater than the number of confirmed cases in each state, providing evidence for a large number of probable symptomatic covid-19 cases that went undetected.”

These were people who showed up at a doctor’s office or clinic with symptoms. Most people with covid-19 probably never sought treatment for the test.

“The increase in ILI across the United States seemed to peak during the week that began on March 15 and subsequently decreased in numerous states the following week; notable exceptions are New York and New Jersey, two of the states that were most affected by the epidemic, which had not started a decline for the week ending March 28, ”the team wrote.

The researchers were unable to count all the cases, so they performed a series of calculations to ensure that their data fit with what is known about state populations and the annual flu epidemic, as well as the hard data that was obtained. from actual tests of patients with coronavirus. They also took into account the growing evidence that people began avoiding hospitals, clinics, and doctor’s offices once it became clear that there was a pandemic, and after pandemic closings began.

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“If 1/3 of the patients infected with SARS-CoV-2 in the USA seeking care, this increase in ILI would have corresponded to more than 8.7 million new SARS-CoV-2 infections in the US during the three-week period from March 8-28, 2020, ”the researchers wrote.

The cases fell after that. “We saw this great spike that ended on March 22 in most places,” Silverman told CNN. The cases have been in decline since then, he said, but the data the team is collecting does not include the past two weeks.

The team is now working to try to get closer to pandemic real-time surveillance. The CDC data comes approximately two weeks after people visit the doctor. They hope their approach, called syndromic surveillance, can complement the data collected from the actual evidence.

“In a dream world, everyone who enters will have a test. We could get a full scope of the pandemic, ”Washburne told CNN.