Around 8.7 Million Americans Had Coronavirus in March but 80% Went Undetected, New Study Suggests

A team of researchers suggest that as many as 8.7 million Americans had coronavirus in March; however, 80% of them were undiagnosed.

The researchers looked at the number of people who went to hospitals and reported influenza-like symptoms but were never diagnosed as coronavirus, influenza or any other viruses that usually comes with the winter season.

They published their study in the journal Science Translational Medicine, wherein they discussed this giant spike of cases in March.

Undetected Coronavirus Cases

Study authors Justin Silverman of Penn State University, Alex Washburne of Montana State University and colleagues at Cornell University, said that the findings of their research support a scenario wherein more than 8.7 million new SARS-CoV-2 infections emerged in the United States during March. They estimated that more than 80% of these cases remained unidentified as the outbreak continues to spread rapidly.

However, only 100,000 cases were officially reported during that time, and the US still reports 2.3 million confirmed cases as of Monday. But it is good to note that there was only a limited supply of test kits during that time, CNN reports.

The team were able to come up with their conclusion based on the data collected by the US Centers for Diseases Control and Prevention for influenza-like symptoms. The CDC uses this data to track the country's annual seasonal influenza epidemic.

It requires doctors to report all cases of people coming in for treatment of the said symptoms such as fever, cough and other flu-related symptoms.

Silverman and his colleagues wrote: "We found a clear, anomalous surge in influenza-like illness (ILI) outpatients during the COVID-19 epidemic that correlated with the progression of the epidemic in multiple states across the US."

The increase in the number of non-influenza outpatients was larger than the number of confirmed cases in each state, which provides evidence of large numbers of probable symptomatic COVID-19 cases that remained undiagnosed.

These were the same people who showed up at a doctor's clinic with symptoms. Unfortunately, most COVID-19 patients do not usually seek treatment or testing for it.

People Avoided Hospital During the Pandemic

The researchers ran a series of calculations to ensure that their data fit in with what is known about the state populations and about the annual flu pandemic, as well as the hard data gathered from actual testing of coronavirus patients since they could not count every single case.

Moreover, they also considered that people started avoiding hospitals, clinics, and doctor's office during the pandemic and after the lockdowns were implemented.

According to the researchers, if 1/3 of patients infected with the virus in the US sought care, the influenza-like illness surge would have corresponded to the 8.7 million new cases of COVID-19 across the US in the three weeks from March 8 to March 28, 2020.

However, cases fell after that, and there was only a huge peak that ended on March 22 in most places. The researchers are now working on getting real-time surveillance of the pandemic and hope their "syndromic surveillance" could complement data collected from actual testing.