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.

The researchers at the Scripps Research Institute in Florida said the mutation affects the spike protein — a structure on the outside of the virus that it uses to get into cells. If the findings are confirmed, it would be the first time someone has demonstrated that changes seen in the virus have significance for the pandemic.