Researchers in Florida say they believe they have shown that the new coronavirus has mutated in a way that makes it more easily infect human cells.
They say more research is needed to show whether the change has altered the course of the pandemic, but at least one researcher not involved in the study says it likely has, and the changes may explain why the virus has caused so many infections in the United States and Latin America.
It's a mutation that scientists have been worried about for weeks.