Irish athletes flying in to London for the World Championships will be housed in a different hotel due to an outbreak of gastroenteritis.
Competition organisers confirmed on Monday night that several London 2017 competitors - staying at the same official team hotel - had suffered gastroenteritis.
Ireland's Thomas Barr was forced to pull out of his 400m hurdles semi-final at the last minute after he fell ill in the early hours of Monday morning.
Irish team management have now made the decision that all athletes coming into the team headquarters for the remaining events of the championship will be housed in a separate hotel to the one where the outbreak took place.
Siofra Cleirigh-Buttner, who goes in the 800m on Thursday, as well as race walkers Rob Heffernan, Alex Wright and Brendan Boyce, all competing on Sunday, will stay in alternative accomodation.
There will also be restricted contact between new members coming in and the rest of the team, who have been offered immediate flights home.
Barr is the only Irish athlete affected.
Public Health England on Tuesday said around 30 people had been affected, with laboratory testing revealing norovirus.
A spokesperson for the Tower Hotel insisted it was "not the source of the illness".
Public Health England London deputy director for health protection Dr Deborah Turbitt said: "PHE has been notified of a confirmed outbreak of norovirus among people associated with the World Athletics Championships.
"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 the London 2017 organisers and the hotel to provide infection control advice to limit the spread of illness."
Norovirus, an unpleasant but rarely serious illness, is often caught through close contact or by touching contaminated surfaces or objects.
A statement from London 2017 read: "There have been a number of cases of gastroenteritis reported by team members residing within one of the official team hotels for the World Championships.
"Those affected have been supported by both team and LOC (local organising committee) medical staff. In addition we have been working with Public Health England to ensure the situation is managed and contained.
"As a result, 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."
