PARIS — French President Emmanuel Macron tested positive for the coronavirus after exhibiting a cough, fever and fatigue, the country's presidential palace announced Thursday.

The 42-year-old president would isolate for seven days but continue to work, the Élysée Palace said.

Macron is the latest world leader to be infected by the virus, following President Trump, Britain’s Boris Johnson and Brazil’s Jair Bolsonaro — all of whom have recovered. In contrast with those leaders, who at least initially played down the threat of the virus, Macron was one of the first heads of state in the West to embrace mask-wearing, and in the spring he presided over one of the tightest lockdowns in Europe. Macron’s age also puts him in a lower risk category.

Hours after his diagnosis was announced, the Élysée released a video of him presiding over a meeting on development via videoconference, though a spokesman told Reuters that all of the president’s upcoming trips — including a visit to Lebanon that was scheduled for next week — had been canceled.

It was difficult to get a sense of his condition from the video. Wearing a dark turtleneck, blazer and N95 mask, Macron read from his notes on international development. He appeared to be more actively engaged than Trump was when the White House released staged photos from Walter Reed National Military Medical Center, and he wasn’t as obviously sick as Johnson was in video released before the British prime minister was hospitalized.

Macron’s diagnosis underscored that France is still contending with a second wave of the virus.

A second national lockdown imposed in late October did manage to curb the spread, but the government had hoped that the daily case load would be lower than 5,000 by the time it lifted movement restrictions this week.

On Wednesday, however, the French health ministry reported 17,615 new cases in the previous 24 hours, along with 264 new deaths. Hospitals had admitted 8,979 new patients, 1,205 of whom were admitted to intensive care units, according to the ministry.

In place of a lockdown, the government has imposed a curfew from 8 p.m. to 6 a.m., and bars and restaurants must stay closed into January.

Macron’s positive test also put other European leaders on alert, given that he interacted in the past week with multiple heads of state or government.

French authorities informed the European Union that they believe Macron was a contagion risk starting Monday evening, meaning that the E.U. leaders who attended a summit in Brussels on Dec. 10 and 11 were not considered contacts, an E.U. official said, speaking on the condition of anonymity to candidly discuss the health situation.

But Portuguese Prime Minister António Costa said he would self-quarantine until the health risk could be assessed because he had been with Macron in Paris on Wednesday. The two gave a news conference in the Élysée Palace courtyard, wearing masks but in proximity, and also attended a working lunch.

“I decided to cancel . . . travel to Africa, as well as the entire public agenda that implies my physical presence,” Costa wrote on Twitter. “I keep all executive activity and the work schedule at a distance. I feel good and without any symptoms.”

Spanish Prime Minister Pedro Sánchez and European Council President Charles Michel were also self-quarantining after meeting with Macron on Monday.

Sánchez wrote on Twitter that he would be suspending his activities until Dec. 24. El Pais reported Thursday that an initial coronavirus test had come back negative.

Michel would quarantine “as a matter of precaution,” although he tested negative Tuesday and “is not considered to be a close contact,” his spokesman, Barend Leyts, wrote on Twitter.

French Prime Minister Jean Castex, who likewise has been in contact with Macron, said he would also be self-quarantining, Agence France-Presse reported.

It was not immediately clear why France believed Macron was contagious starting Monday evening.

Ahead of last week’s E.U. summit, some diplomats were concerned about the health risks of an in-person meeting. Two of the 27 country leaders had to miss the gathering: Croatia’s was sick with the coronavirus, and Estonia’s was quarantining.

The E.U. official said that sanitary measures were taken at the summit and that no other participant had tested positive.

In any case, not all European leaders appeared to trust the Élysée’s assurances. Belgian Prime Minister Alexander De Croo said he was being tested for the virus and would quarantine until he receives the result, after sitting in a room with Macron — along with most of the rest of Europe’s leaders — for almost 24 hours straight starting the afternoon of Dec. 10.

On Wednesday, the day before his diagnosis, Macron held a cabinet meeting, although it was not immediately clear whether it took place in person and if so whether all participants wore masks. The Élysée Palace did not immediately respond to questions about that meeting.

Late Thursday, the Élysée confirmed that Macron would isolate at a French presidential retreat at Versailles, outside the French capital, while first lady Brigitte Macron, who initially tested negative, would remain in Paris.

Vaccination in France is set to begin in late December or early January for high-risk groups and health-care workers before expanding to the broader population between April and June. It will not be mandatory, Macron has said.

Macron’s diagnosis raised immediate questions about the handling of Brexit negotiations, which need to be concluded within days if there is any chance of Britain and the European Union ratifying a trade deal by Dec. 31, the day London will sever its final ties with the bloc. Leaders had previously floated the possibility of an additional in-person summit in the next two weeks to finalize a deal.

European policymakers have complained that negotiations about thorny issues are nearly impossible when they are conducted virtually, as has mostly been the case since March.

Macron has been one of the most stubborn European leaders during Brexit talks, and his sign-off is crucial to any Brexit deal.

Birnbaum reported from Brussels. Rick Noack in Berlin and Teo Armus in Washington contributed to this report.