Medical researchers say the novel coronavirus likely circulated undetected for weeks in New York beginning in February — long before New York confirmed its first COVID-19 case on March 1. Two separate teams of researchers say genetic material taken from thousands of patients shows the main source of early infections came from Europe, and not from Asia. The finding undermines President Trump’s argument that his ban on travelers from China in late January delayed the arrival of the coronavirus in the U.S. It also underscores how a critical lack of testing laid the seeds for an explosion of COVID-19 illnesses and deaths in New York and beyond.

Meanwhile, the National Academy of Sciences warns the spread of the coronavirus is unlikely to slow as springtime temperatures return to the Northern Hemisphere.