As Olympic hopefuls around the world continue training for the Summer Games, conditions on the ground in Tokyo have worsened in recent days, escalating health and safety concerns surrounding the world’s biggest sporting event.

While coronavirus infection rates in the United States largely have plateaued and millions are getting vaccinated each week, Tokyo saw its highest number of covid-19 cases in two months, and government officials are considering tightening restrictions around the Japanese capital again. While recent infection rates there are still significantly lower than in the United States and much of Europe, Japan’s vaccine rollout has been particularly slow, with less than 1 percent of the population having received a coronavirus vaccine dose.

The continued spread of the virus has serious implications for Olympic organizers. A trio of test events reportedly were canceled, and this week the Olympic torch relay was moved away from the public streets in Osaka, which saw a record-high number of cases. Many of those cases involved variants of the coronavirus, leading health officials to warn the situation in Tokyo probably will get worse before it gets better.

Susanne Lyons, chair of the U.S. Olympic and Paralympic Committee board, said Wednesday that Tokyo’s Olympic preparation “has been a little bit like Sisyphus rolling the boulder up the mountain,” but she remained optimistic this summer’s event can be successfully staged.

“At this point in time, we do not see anything that does not say that we can’t go forward,” said Lyons, speaking to U.S. reporters during the USOPC’s virtual media summit. “But we have to be realistic and keep looking at the science and the situation on the ground. I can tell you that the athletes are trying very hard not to focus on any changes in the plan.

“We’re realists, and we understand the health situation is not in anyone’s hands,” she continued, “but we believe this can be responsibly and safely accomplished.”

The lingering virus promises to impact nearly every facet of these Olympics. Next Thursday marks the 100-day out mark for the start of the Tokyo Games, an ever-shrinking window for organizers to prepare and establish safety precautions. This week, North Korea became the first country to pull out of the Tokyo Games, reportedly because of covid-19 concerns.

Many American athletes’ Olympic preparations involve seeking out vaccination shots. While inoculation is not required, Tokyo organizers have urged athletes to do so. Several U.S. athletes who met virtually with reporters Wednesday said they had received at least one shot.

“My thought process was it’s not just for me, but it’s for everyone,” gymnast Yul Moldauer said, “and it’s for all the athletes. . . . For me, I didn’t even think that I was not going to get it, because I knew this was a bigger issue than just myself.”

Gymnast Simone Biles said she plans to get vaccinated soon and “it’s good for athletes to become advocates for that.” Sprinter Allyson Felix, who’s targeting her fifth Olympics, is hopeful she will get a vaccine shot well before the U.S. track and field trials in June.

“I’m just waiting for that opportunity, and thankfully my parents have been vaccinated and everyone is doing really well in my family,” said Felix, who has won nine Olympic medals, “and looking forward to when it’s my turn.”

Athletes say they have considered the possibility of side effects and missed training, and several have timed their vaccination shots around travel and competition schedules. But they also have seen friends and teammates deal with symptoms of the virus and have weighed likely health benefits with any misgivings.

“I wasn’t going to get it,” said Naya Tapper, who plays wing for the U.S. women’s rugby team, “but going into the Olympics and thinking about other people staying safe, I think it’s important to do so.”

U.S. Olympic officials say they aren’t tracking which American athletes get the vaccine and won’t require anyone to receive it before heading to Tokyo. While athletes in some countries are relying on their Olympic or government officials to assist in access to the vaccine, the USOPC has urged its athletes to pursue any options available to them locally or through medical providers.

Tokyo organizers decided last month to allow only Japanese spectators into Olympic events this summer. Even as athletes and other attendees can expect heavy restrictions in Tokyo, safety concerns remain for Japanese volunteers, workers and spectators. Japan has been vaccinating only health-care workers, though people who are 65 and older will become eligible starting next week, followed by those with certain underlying conditions.

Tokyo was scheduled to host test events in the coming weeks for diving, artistic swimming and water polo. In canceling a World Cup diving event, FINA, the international governing body for aquatic sports, cited poor covid-19 precautions. According to the BBC, FINA said in a letter that Japanese organizers could “not properly ensure health and protection guarantees to participants.”

That prompted some red flags across the Olympic world. Still, officials in the United States and worldwide have continued to express nothing but optimism publicly, noting the landscape will continue to shift.

“I think this continues to evolve very, very rapidly over the next 100-plus days,” Lyons said. “I think we’ll continue to see more and more light at the end of the tunnel. I think again we have every expectation that if the proper precautions are taken, we can have a successful Games.”

Emily Giambalvo, Roman Stubbs and Adam Kilgore contributed to this report.