Millions of people in the U.S. were infected by the novel coronavirus in March even though they were not diagnosed with COVID-19. That’s according to a new publication co authored by a researcher at Montana State University.
The study published in the journal Science Translational Medicine says over 80 percent of the infections in the U.S. went undetected during a three week stretch in March. That translates to more than 8 million people with COVID-19.
Alex Washburne, a research scientist in MSU’s Department of Microbiology and Immunology and a contributor to the study, says a shortage of tests played a role in undetected cases.
“But we also missed these patients just because of the difficulties of diagnosing disease and tracing it down to one cause and not another for something that looks so similar to the flu and then arrived on our shores at a time when there still was flu and other endemic respiratory pathogens,” Washburne says.
Washburne and his colleagues at Pennsylvania State and Cornell pulled data from weekly state and federal reports over the last decade showing the number of patients at medical clinics with influenza like illnesses.
“We kept following our feet and that led to this finding of this surge.”
He says the number of people going to medical clinics across the country with influenza like illnesses in March was well above the seasonal average. Washburne says the team concluded the surge was due to undiagnosed COVID-19 cases.
The team then created a model based on prior studies on the rates of asymptomatic cases of COVID-19 and the percentage of people who do not go to a health care provider when they are sick.
“Understanding the number of people who are infected in the U.S. is important, primarily at this stage because it helps us understand the severity of the disease and helps us understand what we are missing when we are only studying the disease from hospitalized patients,” Washburne says.
Washburne adds this study didn’t provide a clear estimate of undetected patients specifically in Montana. He’s working on a disease outbreak warning system for the state and looking at spikes of patient cases with similar symptoms in a community, which could help predict future epidemics and pandemics.
He says that will allow public health officials to respond more quickly and funnel resources to the places that need them most.