(CNN) There's new evidence that the coronavirus may have been in France weeks earlier than was previously thought.
Doctors at a Paris hospital say they've found evidence that one patient admitted in December was infected with Covid-19. If verified, this finding would show that the virus was already circulating in Europe at that time -- well before the first known cases were diagnosed in France or hotspot Italy.
"Covid-19 was already spreading in France in late December 2019, a month before the official first cases in the country," the team at Groupe Hospitalier Paris Seine in Saint-Denis wrote in a study published Sunday in the International Journal of Antimicrobial Agents.
The first official reports of Covid-19 in France were reported on Jan. 24, in two people who had a history of travel to Wuhan, China.
Intensive care specialist Dr. Yves Cohen and his hospital colleagues wrote that they decided to check the records of earlier patients, in case the virus had been spreading undetected.
Researchers in the US have also started finding evidence that the virus was infecting and killing people earlier than the country's first reported cases.
The French team looked at people admitted to the hospital with flu-like illness between December 2 and January 16 who were not ultimately diagnosed with influenza. They tested frozen samples from those patients for coronavirus.
"One sample was positive taken from a 42 year old man born in Algeria, who lived in France for many years, and worked as a fishmonger," the team wrote. "His last trip was in Algeria during August 2019."
The man had not been to China, and one of his children had also been sick, the team reported.
"Identifying the first infected patient is of great epidemiological interest as it changes dramatically our knowledge regarding SARS-COV-2 and its spreading in the country. Moreover, the absence of a link with China and the lack of recent travel suggest that the disease was already spreading among the French population at the end of December, 2019," they wrote.
Europe did not start reporting cases of coronavirus until January. In Italy, the European country hit hardest by the virus, the first two cases were reported on Jan 31, in two Chinese tourists in Rome. The first known community transmission was recorded at the end of February in Codogno, northern Italy.
Correction: This story has been updated to reflect when the study was published online.