According to researchers, at least two patients in a botulism outbreak in France remain in hospital.

The study covered eight individuals from four countries admitted to the intensive care unit at Bordeaux University Hospital, wher six required invasive mechanical ventilation. Cases reported consuming locally produced canned sardines at a Tchin Tchin Wine Bar restaurant. 

As of Oct. 12, six of them had been discharged, but two people still needed mechanical ventilation, according to the study published in the journal Eurosurveillance.

In September 2023, a botulism outbreak affecting 15 people occurred in Bordeaux during the Rugby World Cup. Sick people came from Canada, France, Germany, Ireland, Spain, the United Kingdom, and United States. One person died.

Bordeaux hospital patients
On Sept. 6, the first patient was admitted to the hospital’s intensive care unit (ICU) in Bordeaux. Because of neurological symptoms, they were initially treated for Guillain–Barré syndrome, but botulism was also suspected. On Sept. 9 and 10, two additional patients were admitted to ICU with similar symptoms. All three were visiting France to attend the rugby tournament or for tourism.

Public health authorities were contacted when an outbreak was suspected on Sept. 10. Patient histories revealed the suspected source of infection was home-canned sardines consumed in the same restaurant in Bordeaux by all three individuals. On Sept. 11 and 12, five more patients, also international visitors in France, were hospitalized with clinical signs of botulism. 

Eight cases were treated in ICU from Canada, France, Ireland, and the United States. Two were male, six were female, and seven were younger than 50; one had an underlying neurological condition.

The median delay between consumption of sardines and symptom onset was 13 hours. Patients were admitted to the ICU with a median delay of 42 hours after the onset of symptoms. Six of eight cases required mechanical ventilation because of respiratory muscle paralysis. Patients were treated with botulism antitoxin with a median time between ICU admission and antitoxin administration of 19 hours.

All eight patients were given botulism antitoxin. One person who visited the hospital’s emergency unit with atypical symptoms such as a sore throat during the outbreak period died a few days later in Ile de France.

Positive patient and food samples
Samples from eight hospitalized cases were sent to the French National Reference Center (NRC) for Anaerobic Bacteria and Botulism. Botulinum neurotoxin (BoNT) type B was confirmed in two cases. It was also confirmed in three other patients using stool samples or rectal swabs. 

Sardines from the restaurant were analyzed at the NRC on Sept. 13 and were positive for BoNT and type B Clostridium botulinum.

Type B toxin is less indicative of an outbreak due to fish consumption than type E toxin. It is possible that the incident could be linked to the use of olive oil and aromatic herbs (marinade) before canning sterilization of the sardines, said researchers.

Santé publique France was notified of the three suspected cases of foodborne botulism on Sept. 11. The same day, measures were taken by the Departmental Directorate for the Protection of Populations of Gironde (DDPP) in the restaurant to stop the outbreak, including the removal of suspected food. The investigation found sardines were prepared and served only at the restaurant and not distributed further. On Sept. 12, the Directorate General of Health (DGS) sent a national alert to all practitioners and reported 10 cases.

On Sept. 13, Santé publique France advised people who had visited the restaurant between Sept. 4 and 10 to contact medical practitioners in case of botulism symptoms. The European Centre for Disease Prevention and Control (ECDC) was contacted on Sept. 13 to assess the possible risk outside France, and the World Health Organization (WHO) was informed on Sept. 14.