London - Several athletes have come down with a stomach bug at the world championships, including medal favourite Isaac Makwala of Botswana.
Makwala pulled out of his 200m heat on Monday and later said he had food poisoning.
"There have been a number of cases of gastroenteritis reported by team members residing within one of the official team hotels," the local organising committee said in a statement, putting a dampener on the 10-day event.
"Those affected have been supported by both team and LOC medical staff."
Makwala wrote on his Facebook page that other athletes were also hit by the bug.
Makwala was expected to be the main challenger to Wayde van Niekerk in both the 200m and the 400m. The 400m final is on Tuesday.
"Let's hope they will allow me to run my final," Makwala wrote.
Van Niekerk certainly wasn't affected by the bug. He easily qualified for the semi-finals of the 200m and is the favourite for gold in Usain Bolt's absence.