By Aimee Lewis and Aleks Klosok, CNN

(CNN) -- Athletes staying at one of the team hotels for the IAAF World Championships in London have been affected by an outbreak of gastroenteritis, officials have confirmed.

Approximately 30 people have fallen ill, with laboratory tests confirming two of those cases as the norovirus -- an unpleasant but rarely serious stomach bug which causes gastroenteritis (diarrhea and vomiting).

One of the stars affected is Botswana's Isaac Makwala, who had to withdraw from the 200m heats Monday after a reported bout of food poisoning.

Makwala, 30, is one of the favorites for gold in Tuesday's men's 400m final, a hotly-anticipated event also featuring Olympic champion and world record holder Wayde van Niekerk.

In a statement on his Facebook page, Makwala said: "According to IAAF medics I am apparently suffering from food poisoning which has affected several other athletes in the athletes' hotel. Let's hope they will allow me to run my final tomorrow (Tuesday)."

Ireland's Thomas Barr withdrew from the 400m semifinals, while German and Canadian athletes also staying at The Tower Hotel near Tower Bridge have reportedly been affected too.

In a statement to CNN, Dr Deborah Turbitt, Public Health England (PHE) London deputy director for health protection, said: "We have so far been made aware of approximately 30 people reporting illness and two of these cases have been confirmed as norovirus by laboratory testing.

"PHE has been working closely with British Athletics and the hotel to provide infection control advice to limit the spread of illness."

Public Health England said most peopled made a full recovery from the illness -- often caught through close contact with someone carrying the virus or by touching contaminated surfaces -- within one or two days without treatment.

Hotel 'not source of the illness'

A spokesperson for The Tower Hotel told CNN it was "not the source of the illness," adding that the hotel was working closely with the sport's governing body, the IAAF, and environmental health officers to investigate the origins of the outbreak.

"We can confirm that regretfully a small number of our guests have been suffering from an illness," a statement read.

"We have followed strict hygiene protocol, ensuring that those affected are not in contact with other guests and all public areas have been thoroughly sanitized.

"We continue to liaise with the medical authorities and the IAAF to ensure the comfort of those guests affected and the health and well being of all our guests remains a priority."

Working to ensure situation is contained

A statement issued by the Local Organizing Committee (LOC) said they had been working with Public Health England to ensure the situation was "managed and contained."

"Further advice and guidelines have been issued to team doctors and support staff -- standard procedure for such an occurrence where a number of teams are occupying championship accommodation," the statement read.

Under IAAF rules, Makwala would not normally be allowed to compete again at the championships after pulling out of an event, but because he missed the heats on medical advice he is expected to able to run, if fit.