Researchers who correctly forecasted the growth of COVID-19 infections over the summer issued a warning Monday that cases could nearly double by Inauguration Day, Jan. 20, when presumptive President-elect Joe Biden is to be sworn into office.

In a study published in the journal Scientific Reports, a team from Washington University in St. Louis used a forecasting model to determine the growth rate of infections over the next two months.

What they discovered was not encouraging.

The model predicts 20 million cases of infection in the United States by Inauguration Day and the end of January, a sharp increase from the 12.3 million infections already affecting the country.

“One of the key reasons for the increased accuracy of this model over other COVID-19 forecasts is that this model accounts for the fact that people live in interconnected social networks rather than interacting mostly with random groups of strangers,” said Raphael Thomadsen, professor of marketing at the university, in a statement. “This allows the model to forecast that growth will not continue at exponential rates for long periods of time, as classic COVID-19 forecasts predict.”

The researchers said the forecast includes current practices of social distancing, such as mask usage and staying 6 feet away from others in public.

“Even small increases in social distancing can have a large effect on the number of cases we observe in the next two and a half months,” Thomadsen said. “Going back to a 50% return to normalcy, which was the average level of distancing in early August, would likely result in 5 million fewer cases by the end of January.”

He added that if additional restrictions were enacted, such as stay-at-home orders, the growth rate of infections would quickly come to a standstill.

“We could effectively squash out the COVID growth within a few weeks if we went back to the levels of social distancing we experienced in April,” he said.

Even with an estimated 8 million additional cases by Inauguration Day, the researchers said that number could be higher in light of increased testing and the holiday season.

A poll from Ohio State University this month found that nearly two in five Americans said they were likely to attend a Thanksgiving gathering with more than 10 people or people outside their family.

“The upcoming holiday seasons will present a great deal of uncertainty to the outlook of the pandemic as people travel more at the end of the year. This will likely make our forecast an optimistic one,” said Meng Liu, assistant professor of marketing.

More than 3 million new cases of infection have occurred in the U.S. since Nov. 1, according to John Hopkins University. Those cases represent a quarter of all cases in the country since the start of the pandemic.

— By Jon Parton, CNS