Model suggests COVID-19 may have been in Colorado as early as January 2020


DENVER (KDVR) — A mathematical model constructed by the Colorado COVID Modeling Team suggests COVID-19 may have been in Colorado in January, three months before the state’s first case was officially confirmed.

The Colorado COVID Modeling Team was assembled to analyze hospitalizations and determine when Colorado would cross certain thresholds in terms of the number of ventilators and ICU beds available.

In September, the group started working on a mathematical model to determine when the first cases of COVID-19 arrived in Colorado.

“There were people inquiring, ‘I had some sort of a cold in January’ or ‘I felt really awful. Did I have COVID?’ The answer is probably not just because the number of people infected at the time,” said David Bortz, an associate professor in the applied mathematics department at the University of Colorado Boulder and a member of the Colorado COVID Modeling Team.

The team examined community spread, built a mathematical model and worked backwards. Bortz said the model suggests COVID may have arrived in Colorado in January.

“Our best guess was that, based on the uncertainty in the model, sometime in January is when it started,” said Bortz. “You could have had one person in early January or a handful of people in late January and get the same result.”

Dr. Elizabeth Carlton is also a member of the Colorado COVID Modeling Team. She said other teams around the U.S. have run similar models with similar results, indicating the virus was spreading in the U.S. before the first cases were officially confirmed.

“All seem to indicate that disease was in the US previous to the first recorded case,” said Dr. Carlton.

Bortz said models suggest people carrying the virus could have entered Colorado over the holidays at the earliest.

“Thanksgiving would be pushing it. That’s some of the early cases even in China so just the odds of someone from there coming directly to Colorado in November or early December is just very, very low based on the mathematics of what we know happened later on,” said Bortz.

As for where Colorado’s first cases originated, Dr. Carlton said models suggest it was most likely in Colorado communities with exposure to the outside world.

“We don’t know when the first infection came to Colorado or where they entered but its plausible to think about our most connected parts of Colorado,” said Dr. Carlton. “Colorado has a lot of connections to the outside world because people come to Colorado to ski. People come to Colorado Springs to train in the military. People come to our universities.”

Dr. Carlton said determining when COVID-19 began spreading in Colorado is key in determining how to bring it to an end.

“What this history teaches us is the importance of investing in surveillance infrastructure. We want to be able to find those cases and know where infections are happening so we can deal with them,” said Dr. Carlton. “We want to learn the history of this virus so we can avoid repeating the mistakes that happen and that we learn from what happened and we do better next time.”

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