An outbreak of the norovirus has struck about 30 athletes and support staff staying at one of the London hotels housing athletes competing in the track and field world championships.

Public Health England confirmed the outbreak of the highly contagious virus, which causes vomiting, diarrhea, a low-grade fever, aches and abdominal pain. The top contender in the 400 meters, Botswana’s Isaac Makwala, was told by International Association of Athletics Federation officials to withdraw from the 200 prelims after vomiting. Because he was given medical dispensation, he will be able to compete in the final. “I could have run. I did my warmup well and I was ready to run,” he told the BBC. “This is bad. Sometimes I feel heartbroken. Yesterday, I was ready for this. I worked hard for this.”

The Tower Hotel, where several German and Canadian athletes also became ill, said that an investigation by the IAAF and health officers showed it was not the source of the outbreak and that public areas of the hotel, which is near Tower Bridge, had been sanitized.

The team from Ireland confirmed that 400-meter hurdler Thomas Barr had been stricken, as had German triple jumper Neele Eckhardt.  “I’m gutted to have to withdraw from the semifinal,” Barr told the Guardian. “My whole year has been focused on the world championships. To not be able to go out and compete for Ireland is beyond disappointing.”

The event, billed as the biggest athletic competition in London since the 2012 Olympics, already has seen one big upset. Usain Bolt lost to Justin Gatlin in his signature event, the 100 meters, in his final competition as a professional track star.

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