Some Americans had antibodies to SARS-CoV-2 in blood samples they gave in January 2020, so they must have got infected in 2019.

I don't know whether there is any chance that some other coronavirus could have triggered formation of antibodies that react to SARS-CoV-2. If not, those Americans must have caught Covid-19 in December.

*'Let Scientific Evidence Determine Origin' of Covid-19, Say Heads of US National Academies.*

A Chinese virologist said this means the investigation of the origin of SARS-CoV-2 should move to the US.

The investigation should study all relevant places and events. Trying to "blame the US" for Covid-19 is as foolish as trying to "blame China" for it. It is foolish to consider this as a matter of rivalry between countries. If any mistakes were made by China, if any mistakes were made by the United States, if any were made elsewhere, the world needs to know what happened and understand them.