A study by French scientists which suggests a man was infected with COVID-19 as early as Dec. 27, nearly a month before France confirmed its first cases, could be important in assessing when and where the new coronavirus emerged, experts said on Tuesday.

A man identified as the patient told a French TV station that he was surprised to learn that he had contracted COVID-19 since he thought he had flu at the time.

French researchers led by Yves Cohen, head of resuscitation at the Avicenne and Jean Verdier hospitals, retested samples from 24 patients treated in December and January who had tested negative for flu before COVID-19 developed into a pandemic.