As U.S. figure skaters test positive, new worries before Winter Olympics.

U.S. Figure Skating on Saturday announced the women’s team heading to Beijing for the Winter Olympics next month. It will include a top-ranked competitor who withdrew from nationals this week in Nashville after a positive coronavirus test, a stark reminder of a resurgent pandemic still capable of disrupting sports events and lifelong dreams.

“Things happen unfortunately, but it is what it is,” Alysa Liu wrote on social media after her withdrawal on Friday. A strong showing this past season on the international circuit, in spite of having to miss nationals, helped solidify her a spot to compete at the Games. Skaters are selected for the Olympic team based on their body of work over the course of a year — the U.S. national championships in figure skating are not an Olympic trial event, as they are in some other sports.

Also named to the women’s singles team were Mariah Bell, the 25-year-old whose victory on Friday made her the oldest female national singles champion in 95 years, and Karen Chen, 22, a 2018 Olympian who finished second to Bell.

Liu, 16, is among at least six skaters who tested positive this week and withdrew from nationals as the highly contagious Omicron variant drives a new wave of infections around the world — just weeks before the Beijing Games are scheduled to begin. Many of the skaters described having adopted stringent measures, including forgoing private lessons at the rink, to avoid just such outcomes.

Amber Glenn, another skater, tested positive and withdrew “with a heavy heart” from nationals, losing what was her last opportunity to impress the Olympic selection committee. On Instagram, she described how she had taken precautions like social distancing and wearing K95 face masks. She said she initially attributed early symptoms to nerves or allergies.

Brandon Frazier, who, with Alexa Knierim, is the reigning national pairs champion, tested positive on Wednesday and withdrew from competition. U.S. Figure Skating will announce the United States’ two Olympic pairs teams on Sunday, and Frazier and Knierim said they had petitioned to be selected for the Games.

It remains unclear, though, how long it will take potential Olympians battling the virus to feel well enough to skate again or to begin testing negative, only adding to the uncertainty as many athletes prepare for travel to Beijing soon.

China has already announced elaborate measures to protect against the coronavirus reaching its own population or participants in the Winter Games, and to ensure those two groups have almost no contact with one another. Last month, Chinese officials detailed some of the strictest rules yet for its own citizens attending the Games.

Spectators — which were already limited to residents of China — will be allowed to clap, but not shout, in support of athletes. Waiters, cleaners and other support staff will not be allowed to leave Olympic venues to visit their families. And any Olympic participants leaving the vicinity for other parts of China will be required to spend at least one week in quarantine, followed by at least two weeks of isolation at home.

Foreign athletes, trainers, coaches, referees, journalists and a few others will be restricted to a “closed loop” of hotels and sports venues, linked by special buses and trains. Everyone will face daily P.C.R. tests.

And still, Chinese officials acknowledged they were bracing for the inevitability that some infections will emerge at the Olympics.