Gastroenteritis affects athletes 'physically and mentally'

Botswana's Isaac Makwala, who is among the favourites for the 400m, withdrew from Monday's 200m heats after a reported bout of food poisoning.

Several German and Canadian athletes staying at the Tower Hotel fell ill last week.

Former sprinter Iwan Thomas explains how the outbreak of gastroenteritis at the official team hotel for the World Championships in London will affect the athletes.