The study suggests that most Covid-19 cases remained undetected

The study suggests that most Covid-19 cases remained undetected

A team of researchers examined the number of people who went to doctors or clinics with patients like the flu, who were never diagnosed with coronavirus, influenza, or any other virus that usually circulates in the winter.

“These findings support a scenario where more than 8.7 million new SARS-CoV-2 infections occurred in the United States during March and estimate that more than 80% of these cases remained unidentified as the epidemic spread rapidly,” said Justin Silverman of the University. Penn, Alex Washburne of Montana State University and colleagues from Cornell University and elsewhere, wrote.

In that period, only 100,000 cases were officially reported, and the U.S. still records only 2.3 million cases as of Monday. But then there was a shortage of coronavirus test kits.

The team used data collected from each state by U.S. Centers for Disease Control and Prevention for a flu-like illness. The CDC uses this data to monitor the annual seasonal flu epidemic. He asks doctors to report all cases of people coming for treatment due to fever, cough and other symptoms caused by the flu.

“We found a clear, anomalous increase in influenza-like outpatient (OR) outbreaks during the COVID-19 epidemic, which correlated with the progression of the epidemic in multiple states across the U.S.,” Silverman and colleagues wrote.

“The attack of outpatients without influenza was much higher than the number of confirmed cases in each state, providing evidence of a large number of probable symptomatic cases of COVID-19 that remained undetected.”

These were people who showed up at the doctor’s office or at the clinic with symptoms. Most people with Covid-19 probably never sought treatment from the trial.

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“U.S. growth OR peaked during the week that began March 15 and then declined the following week in a number of states; notable exceptions are New York and New Jersey, the two countries hardest hit by the epidemic, and did not decline until the week that ended March 28, ”the team wrote.

How coronavirus tests disintegrated precious time

The researchers could not count each individual case, so they performed a series of calculations to ensure that their data fit into what is known about the state’s population and annual flu epidemic, as well as with difficult data collected by actual testing of coronavirus patients. They also took into account the growing evidence that people started avoiding hospitals, clinics and doctor’s offices after it became clear that there was a pandemic and after the pandemic was canceled.

“If 1/3 of patients infected with SARS-CoV-2 in the U.S. had sought care, this OR rush would have matched more than 8.7 million new SARS-CoV-2 infections across the U.S. during the three-week period from March 8 . to March 28, 2020, “the researchers wrote.

Cases fell after that. “We’ve seen this huge climax that ended on March 22 in most places,” Silverman told CNN. Cases have been declining since then, he said – but the data the team is collecting does not include the last two weeks.

The team is working today to try to approach the pandemic in real time. Data from the CDC comes about two weeks after people come to see a doctor. They hope that their approach – called syndrome surveillance – could complement the data collected by actual testing. “In the world of dreams, everyone who calls has a test. We would be able to get the full scope of the pandemic,” Washburne told CNN.

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