Doctors are looking into whether the 43-year-old man might be France's "patient zero", the term used to describe the first human infected by a disease in an outbreak.
Dr Yves Cohen, head of emergency medicine at Avicenne and Jean-Verdier hospitals near Paris, told local media his medical team had revisited test results from 24 patients with respiratory infections who had tested negative for flu and other kinds of coronavirus back in December and January.
Among them was a male patient's swab that tested positive for Covid-19 on repeated tests.
The patient, Amirouche Hammar, who has since recovered, was ill for 15 days and infected two of his children.
His wife, who works in a fish stall at a local supermarket near an airport, was not taken ill.
The man told French media BFMTV he had what are now familiar coronavirus symptoms: a dry cough, fever, fatigue and severe breathing difficulties.
He said he at first thought he had flu but after his symptoms worsened, he decided to go to hospital.
At that time, only China was thought to be affected by the pandemic; the World Health Organization declared the existence of a new coronavirus on January 12 and the first death was announced the following day.
The first case of someone suffering from Covid-19 can be traced back to 17 November in China, according to local media reports on unpublished Chinese government data although authorities gave WHO the first official diagnosed case as December 8.
Chinese authorities did not publicly acknowledge there was human-to-human transmission until 21 January.
Mr Hammar told BFMTV he does not know how he could have contracted Covid-19, he had no connection to China and had not travelled abroad before falling ill in December.
Dr Cohen said he had questioned whether Mr Hammar's wife Fatiha had been exposed to fish products from China, where the virus originated.
She said: "We serve customers who come directly from the airport, with the suitcases."
Mr Hammar was tested in hospital on December 27, and Dr Cohen said the test had been repeated several times to confirm the result.
"But perhaps there are other patients in other regions." he said. "The virus might still be circulating."
As of Monday, France has reported more than 168,000 Covid-19 cases and 24,898 deaths.
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