The number of people affected by illness at the World Championships has risen to 50, with four confirmed cases of norovirus, Public Health England announced today.
Illness has affected athletes and officials at the championships, taking place at the London Stadium until Sunday.
PHE 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 IAAF World Championships London 2017.
"We have so far been made aware of approximately 50 people reporting illness and four of these cases have been confirmed as norovirus by laboratory testing.
"PHE has been working closely with the London 2017 organisers and venues to provide infection control advice to limit the spread of illness."
Public Health England had issued a statement on Thursday saying there had been 40 affected and three norovirus, and the latest update shows the vomiting bug is lingering on the final weekend of the championships.
London 2017, the championship organisers, announced on Monday night that several competitors - staying at the same official team hotel - had suffered gastroenteritis.
A spokesperson for the Tower Hotel on Tuesday morning insisted it was "not the source of the illness".
Public Health England on Tuesday said around 30 people had been affected, with laboratory testing revealing norovirus in two cases, and later told Press Association Sport that it believed there were connected cases at other hotels accommodating those involved in the championships.