American medics officially registered their first COVID-19 patient on January 19, 2020, but the findings in a paper published in the journal Clinical Infectious Diseases suggest the virus may have been circulating in the US prior to that.
The researchers studied almost 7,400 blood donations made in nine US states between December 13, 2019 and January 17, 2020.
Evidence of COVID-19 bodies antibodies, the presence of which suggest a person had contact with the virus, were present in 106 of those samples, according to the study.
This means coronavirus could have been in the US a month before it saw its first confirmed case, and weeks before the Chinese authorities announced the infection in the city of Wuhan.
The analysis of hospital data from across the US in late 2019 also showed a spike in flu patients, many of whom had “heavy coughing” and other severe respiratory symptoms.
European researchers have also speculated that coronavirus had been present in their countries before China officially announced the outbreak of the new strain.
A French survey has discovered there were COVID-19 antibodies in blood samples taken in early December 2019. A similar study carried out by their Italian peers revealed that samples in Italy were already showing antibodies in September.
Spanish virologists, meanwhile, found traces of coronavirus in sewage water samples collected in March 2019 – a full nine month before the events in Wuhan.
The precise origins of coronavirus are currently unknown, but the US has been making active attempts to blame it on China since the start of the pandemic. President Donald Trump has often referred to the disease – which has so far infected more than 13.8 million people, and killed more than 271,000 in America – as the “Chinese virus,” provoking vehement protest from Beijing.