Botswana's Isaac Makwala qualified for the men's 200m semi - finals in a race he ran alone after he was declared medically fit to contest at the world championships here.
Makwala clocked 20. 20 seconds to qualify for the semi - finals on Wednesday night, reports Xinhua news agency.
The 30 - year - old was forced to pull out of the 200m heats on Monday as he was among 30 athletes and support staff staying at one of the team hotels for the Worlds in London falling victim to a suspected outbreak of norovirus.
He also quit the 400m final on Tuesday.
"Given his quarantine period expired at 14:00 hrs today (August 9) and following a medical examination which has declared him fit to compete, we have agreed under our existing rules that assuming he makes the qualification time, he will run in the 200m semi - finals, " the organisers said in a statement on Wednesday.
"No athletes already qualified for the semi - final will be adversely affected, " they added.