French authorities confirmed the first cases of the Omicron version of the coronavirus in mainland France on Thursday, but their alert remained focused on a wave of infections fueled by the Delta variant.

France on Wednesday reported nearly 50,000 new cases of the virus in 24 hours, the highest daily total since spring. The number of reported cases per 100,000 people rose from less than 100 to more than 300 in the past month.

“We have to anticipate – there are still a lot of uncertainties,” Jean-François Delfraissy, the chairman of the French government’s scientific advisory board on Covid-19, told BFMTV on Thursday, referring to Omicron. “But let’s not fight the wrong fight. The real fight, the real enemy, is the fifth wave with the Delta variant.

The outbreak has alarmed the French authorities, even if they have so far ruled out a return to blockages or business closures. Mr Delfraissy said the cold had pushed people inside and social distancing was no longer scrupulously observed. The average number of new hospital admissions, including intensive care, has also increased by around 40% in recent weeks, according to official statistics.

But hospitalizations are still below peaks seen in previous waves, thanks to an immunization rate of 75 percent of the entire population, and Mr Delfraissy said that if people exercise renewed vigilance – in avoiding rallies, working from home when possible and wearing masks more often – France could be spared the worst results.

“Christmas is not in danger if we are all careful,” he said.

The French government, which recently made all adults eligible for booster shots, has avoided imposing vaccines, arguing the coercion would be counterproductive. Olivier Véran, the Minister of Health, told reporters this week that a “more powerful incentive” was the national health pass, which is required to access museums, restaurants, cinemas and other public places.

Thursday’s announcement of two cases of Omicron in mainland France added to concerns, although scientists are still trying to understand the threat posed by the variant.

The health authority for the ÃŽle-de-France region, which includes Paris, said the Omicron variant was found in a man in his 50s who returned from Nigeria last week and tested positive for Covid-19 after disembarking from his flight, although he showed no symptoms. The man, who was not vaccinated, was isolating himself at his home, officials said.

In eastern France, health authorities in the Grand-Est region said in a statement that Omicron was detected in a woman in her 40s who returned from South Africa last week. The woman has been vaccinated but is showing symptoms and has isolated herself at home.

Previously, France had only confirmed one case of the Omicron variant, in the overseas department of Réunion, in the Indian Ocean.

The uncertainty as to the real dangerousness of the Omicron prompted the French authorities to suspend flights with 10 countries in southern Africa, where the variant was detected for the first time. Flights will be allowed to resume from this weekend, but with some restrictions for travelers still in place. France will also require all visitors arriving from outside the European Union to provide a negative result for the coronavirus test, regardless of their vaccination status.