The timeframe of the Covid-19 outbreak in France has been edged back almost a month before the French authorities confirmed the first case in the country.

A hospital in the Parisian suburbs has retested a sample taken from a man with a flu-like illness just after Christmas and discovered he was actually infected with Covid-19 as early as December 27, 2019.

Prior to this discovery, France’s first confirmed case was in late January 2020. In fact, this newly identified case is four days before the World Health Organization was even notified about mysterious pneumonia cases being detected in the Chinese city of Wuhan.

Reported in the International Journal of Antimicrobial Agents, doctors from University Hospitals Paris Seine-Saint-Denis reviewed medical records and samples taken from intensive care patients admitted with influenza-like illnesses between December 2, 2019 and January 16, 2020. Out of the 14 swabs reanalyzed using a polymerize chain reaction (PCR) test, they identified one positive Covid-19 result from a 42-year-old man who came to the emergency room on December 27 with a dry cough, headache, blood in his mucus, and a fever. On a second look, the doctors also noticed his clinical signs and medical scans were much like those seen in Covid-19 patients.

The report states the man was born in Algeria but had lived in France for many years where he worked as a fishmonger. He had reportedly never been China, but his last trip abroad was to Algeria during the summer of 2019. The report also notes that one of his children presented with an influenza-like illness around the time the man developed symptoms. However, his wife appeared to be completely asymptomatic.

"He was amazed, he did not understand how he had been infected. We put the puzzle together, he had not made any trips, the only contact is that made by his wife," Dr Yves Cohen, head of emergency medicine at Avicenne and Jean-Verdier hospitals in Paris, told French news channel BFM TV.

"Then we learned, by chance, that she [the patient's wife] works in sushi sales alongside people of Chinese origin,” Dr Cohen speculated. 

"He may be the 'zero patient,' but perhaps there are others in other regions. All the negative PCR for pneumonia must be retested. The virus was probably circulating," he added.

The US also recently revised the timeline of its Covid-19 outbreak after autopsies on two people who died in California’s Santa Clara County on February 6 and February 17 revealed they died from Covid-19. It's entirely possible that more early cases of Covid-19 will be unearthed worldwide, although, based on the evidence currently available, it seems to be unlikely there were a significant number of Covid-19 cases in Europe and North American in December and November 2019. 

"I believe at the end of this, when we do look back – and we will – we will probably find that this disease was here earlier than we thought," Dr Georges Benjamin, executive director of the American Public Health Association, told USA Today in early April 2020. He added it's "plausible but not likely" that Covid-19 was in the US in November and December.