The Centers for Disease Control and Prevention (CDC) has repeatedly said the first case of COVID-19 was diagnosed in the U.S. on Jan. 19, 2020.

Now, the CDC is amending that timeline.

A new study shows testing found COVID-19 infections in the U.S. in mid-December 2019. The study, which was published Monday, identified 106 infections from 7,389 blood samples collected from donors in nine U.S. states between Dec. 13 and Jan. 17. The samples, collected by the American Red Cross, were sent to the CDC for testing, which showed antibodies in 39 samples from California, Oregon, and Washington state collected between Dec. 13-16.