Why was the positive rate in a study of COVID-19 antibody test higher in blood samples collected in America back in 2019 and early 2020, compared with that in Hubei-ex-Wuhan after the pandemic outbreak? Could it be a result of lacking tests? More reports are directing at earlier cases of COVID-19 on U.S. soil. Which country really was "ground zero"? The point is, the U.S. has to do more to earnestly investigate the origins of the virus.