During the coronavirus's first month in the United States, thousands of cases across the country likely went undetected.
But research in the journal mBio by the Arizona COVID-19 Genomics Union show that wasn't the case in Arizona.
A team from the Translational Genomics Research Institute and Arizona's three public universities finds the state had no COVID-19 cases, known or unknown, until at least mid-February.
A mutation "clock" derived from almost 3,000 samples shows that, by early April, 11 viral lineages were present — all of them unrelated to the first case found in an Arizona State University student isolated in late January.
University of Arizona researcher Brendan Larsen said that shows public health interventions can work.
"And in fact we did not detect any viruses that descended from the first, initial introduction," he said.
