Over 350 people ‒ 205 staff and 160 members of the public reported feeling ill – although the cases have not been officially confirmed as norovirus, according to Public Health England (PHE).
Sites affected but now reopened were Manchester, Brighton, Cardiff and London branches in White City and St Paul’s.
Canary Wharf is expected to open later today while Soho, Oxford Circus and Covent Garden remain closed.
Wahaca is currently conducting its own tests along with PHE and local environmental health officers to track down the source of the outbreak.
Wahaca co-founders Mark Selby and Thomasina Miers called it an ‘unprecedented incident’ in the group's nine years of trading, but said the situation was under control.
When it became obvious that the illnesses were not isolated, Wahaca said it took ‘precautionary measures’, voluntarily closing the nine affected restaurants.
Selby and Miers said that in addition to this Wahaca carried out anti-viral deep cleaning in all its restaurants whether affected or not. It also ensured that any staff member who had reported the illness remained off site until their symptoms had ceased for at least 48 hours.
They praised their teams for working ‘tirelessly’ to ensure they limited the risk to customers and staff.
Selby and Miers said: “We are incredibly sorry that people have been unwell. In the nine years since we first opened Wahaca we have never had such an unprecedented incident, and we are doing everything we can to get to the bottom of how this may have happened.”
Source ‘not confirmed’
Deborah Turbitt, London deputy director for Health Protection for PHE, said: “We are working closely with environmental health officers and the restaurant chain to investigate. Currently, the source of the outbreak is not confirmed and this remains under investigation.
“Norovirus can be very unpleasant but is rarely serious. Most people make a full recovery within one or two days, without treatment.”
What is norovirus?
Norovirus is one of the most common stomach bugs in the UK, which causes diarrhoea and vomiting.
It can be caught if small particles of vomit and poo from an infected person get into the mouth. This can be by close contact, touching contaminated surfaces or eating contaminated food.
It is most infectious from when symptoms start until 48 hours after the symptoms have passed.