An outbreak of foodborne botulism in France has highlighted the effectiveness of using credit card data to identify potential patients, according to researchers.

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 the United States. One person died. Patients reported consuming locally produced canned sardines at Tchin Tchin Wine Bar restaurant. 

A search for people who had consumed the sardines was done using data from restaurant credit card receipts, according to the study published in the journal Eurosurveillance.

Getting contact details through the use of credit cards
By screening meal orders and card receipts, researchers found 29 customers had ordered canned sardines. A dozen had already been identified as suspected cases. French or British health authorities contacted another 14 but they did not have any symptoms. However, three were symptomatic British citizens who were referred to emergency care in the UK and received botulinum antitoxin.

Identification of customers was possible after looking at credit card payments and retrieving personal contact information via the credit card companies.

Given the severity of botulism, card companies cooperated with health authorities and contacted the identified customers for approval before forwarding contact details. This enabled three British people unaware of their illness to be sent to an emergency unit for administration of botulism antitoxin.

By the time the outbreak was recognized, most exposed people had returned to their home countries. However, all were identified via credit card companies and provided with a public health emergency contact should symptoms occur.

Data such as loyalty cards or receipts are frequently used in outbreak investigations to identify food products purchased. These methods complement other means in epidemiological investigations. However, because of data protection regulations, access to personal data through credit card receipts is not always feasible promptly. This practice cannot be routinely applied during epidemiological investigations given the sensitivity of the data, said scientists.

Botulism type not usually linked to fish
All suspected patients had visited the same restaurant in Bordeaux on different dates and consumed canned marinated sardines. These were part of a batch made by the restaurant on Sept. 1 and served between Sept. 1 and 10. Several cases reported a bad taste or smell from the product marinated in oil and herbs.

People fell sick between Sept. 5 to 12. The median age of cases was 36 but ranged from 30 to 70. Of all cases, seven were female, and eight were male. Thirteen were hospitalized, with six requiring invasive mechanical ventilation. Of the 15 suspected cases, 10 were laboratory-/confirm/ied.

A previous study in the same journal gave more details on eight individuals from four countries who were admitted to the intensive care unit at Bordeaux University Hospital.

Inspectors visited the restaurant, and while they did not identify any deviations in food storage, they noted incorrect sterilization techniques in the preparation of canned food.

The sardine samples from five different jars tested positive for type B Botulinum neurotoxin (BoNT) and type B Clostridium botulinum. All other food samples, including marinade ingredients, were negative.

Previous reports of botulism caused by fish- and other marine products have been linked to type E BoNT, while type B has primarily been associated with processed pork products.

“This outbreak of foodborne botulism in France highlights both the effectiveness of using credit card data to identify exposed persons and possibly prevent severe cases rapidly. It also underlines the importance of efficient international collaboration networks, particularly in mass gatherings when people from many countries can be exposed, such as in the coming Olympic Games organized in France in the summer of 2024,” said researchers.