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|Venue: London Stadium Dates: 4-13 August|
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Botswana's Isaac Makwala was ruled out of Tuesday's 400m final despite insisting he was fit after an outbreak of the norovirus bug.
The 30-year-old, who was also pulled out of the 200m heats on Monday, was withdrawn by organisers the IAAF "due to a medical condition".
Makwala had earlier told the BBC he would be "devastated" to miss out.
Public Health England says 30 athletes and support staff have been affected by sickness at the Tower Hotel in London.
Makwala was considered to be a leading challenger to Olympic champion and world record holder Wayde van Niekerk in the 400m.
He turned up at the stadium before the race but was ordered to leave by IAAF officials.
He had admitted to vomiting before the 200m heats, but said he was not tested.
"I could have run. I did my warm up well and I was ready to run. I feel ready to run today, tonight," he said.
"This is bad. Sometimes I feel heartbroken. Yesterday, I was ready for this. I worked hard for this."
IAAF spokeswoman Jackie Brock-Doyle told BBC Sport: "It's a sad case but we have to follow process for the health and well-being of all athletes.
"All processes have been followed, clear statements released and very clear guidelines issued to team managers and doctors on Sunday.
"We can't go into details of athletes' conditions. It's better the statements and Public Health England statement stand."
Who has been affected?
Several German and Canadian athletes staying at the Tower Hotel fell ill last week.
A further 30 Germans due to arrive on Tuesday will be moved to other hotels.
German triple jumper Neele Eckhardt collapsed but was well enough to compete on Saturday, and took part in Monday's final.
The Ireland team, who are also staying at the hotel, have confirmed that one athlete - 400m hurdler Thomas Barr - has been affected.
The Tower Hotel said investigations conducted with environmental health officers and athletics' governing body the IAAF had shown the hotel was "not the source of the illness". That has also been confirmed by Public Health England.
Michael Johnson, four-time Olympic gold medallist athlete
The IAAF may soon realise they have got this horribly wrong as to why they have chosen to disqualify Makwala.
Does this apply to other athletes? If you collapse, you are OK but if you vomit you aren't OK?
Has he been advised not to be around other athletes?
There is a lot of inconsistency here.
And then of course, there is the elephant in the room - Wayde van Niekerk's only challenger has been pulled out of both the 200m and 400m. The conspiracy theories will come out of the silence.
How do you catch norovirus?
Michelle Roberts, BBC Health
Stomach bugs that cause diarrhoea and vomiting are very common and easy to catch. You can get them from eating contaminated food or through contact with people who have got gastroenteritis.
If that infected person doesn't wash their hands before handling your food or touching objects and surfaces that you then touch, there's a good chance you could get sick too.
A person with gastroenteritis is most infectious from when their symptoms start until a couple of days after all their symptoms have gone.