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Situation at a glance
On 12 September 2023, local public health authorities in France identified a cluster of 10 cases with suspected botulism, including one death. As of 14 September 2023, the National IHR Focal Point for France has notified WHO of a total of 15 cases of suspected botulism, including one death, reported in Bordeaux and Ile-de-France.
The epidemiological investigations indicated that the source of infection is the consumption of homemade preserved sardines , on different dates, at the same restaurant in Bordeaux during the week of 4–10 September 2023. The food item was made at the restaurant for consumption on premises.
Due to the incubation period of up to eight days and the restaurant attracting international visitors during the Rugby World Cup, there is a possibility that additional cases among international visitors may be reported in France, or possibly outside France as travellers returned home, until 18 September.
Description of the situation
On 12 September 2023, local public health authorities in France identified a cluster of 10 cases with suspected botulism, including one death.
As of 14 September 2023, the National IHR Focal Point for France has notified a total of 15 cases of suspected botulism, including one death, reported in Bordeaux and Ile-de-France. Of these 15 cases, 10 have been hospitalised, with eight patients being admitted to an Intensive Care Unit. Fourteen out of the 15 cases are reported among foreign citizens identified from six countries in addition to France. These include Canada, Germany, Greece, Ireland, the United Kingdom of Great Britain and Northern Ireland, and the United States of America. All suspected cases consumed the same product (sardines in jars) on different dates at the same restaurant in Bordeaux during the week of 4–10 September 2023. The epidemiological investigations indicated that the source of infection is the consumption of homemade preserved sardines. The food item was produced and served at the restaurant.
Epidemiology of the Botulism
Botulism is a serious neurological condition caused by a very potent toxin produced by the bacterium Clostridium botulinum . It develops particularly in poorly preserved foods. Human botulism may refer to foodborne botulism, infant botulism, wound botulism, and inhalation botulism or other types of intoxication.
Foodborne botulism is a serious, potentially fatal disease. It is an intoxication caused by ingestion of potent neurotoxins—the botulinum toxins—formed in contaminated foods. Person-to-person transmission of botulism does not occur. The manifestations, or symptoms, of intoxication can vary, and is characterized by descending, flaccid paralysis that can cause respiratory failure. Early symptoms include marked fatigue, weakness and vertigo, usually followed by blurred vision, dry mouth and difficulty in swallowing and speaking. Vomiting, diarrhoea, constipation and abdominal swelling may also occur. The disease can progress to weakness in the neck and arms, after which the respiratory muscles and muscles of the lower body are affected. There is no fever and no loss of consciousness. Symptoms usually appear from several hours up to 8 days following consumption of contaminated food.
Although botulism outbreaks are relatively rare, they are considered public health emergencies that require rapid recognition to identify the disease source, distinguish outbreak types (between natural, accidental or deliberate), prevent additional cases and effectively administer treatment to affected patients. Successful treatment depends significantly on early diagnosis and the rapid administration of the botulinum antitoxin and intensive respiratory care.
Incidence of botulism is low, but the mortality rate is high if prompt diagnosis and appropriate, immediate treatment is not given. The disease can be fatal in 5% to 10% of cases.
Public health response
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On 11 September, food and serum samples were shipped to the French National Reference Center for Anaerobic Bacteria and Botulism, Institute Pasteur, Paris , and botulinum toxin was confirmed in serum samples and in a food sample (sardines) on 14 September 2023.
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The local health authorities inspected the restaurant and all products prepared by the restaurant have been recalled. On 13 September, the local health authorities held a press conference and informed the local healthcare professionals.
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The national health authorities have issued risk communication advice to sensitize the health care workers about the symptomatology and treatment.
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Information on cases reported among citizens from foreign countries have been shared with the relevant health authorities in those countries.
WHO risk assessment
Local investigations have identified an estimated 25 persons through credit card receipts who have been exposed (i.e., who likely consumed the suspect food item). The exposure occurred at local level and measures have been implemented to eliminate the source of infection including the removal of the suspected food item, which was not distributed outside the venue. However, given the ranging incubation period of botulism—up to eight days—and that not all customers of the restaurant in Bordeaux may have been identified despite efforts, further cases linked to this event may still occur. This outbreak has occurred at the same time as the Rugby World Cup held from the week of 4 September 2023 attracting followers and rugby teams from all over the world.
WHO advice
Prevention of foodborne botulism is based on good practice in food preparation particularly during heating/sterilization and hygiene. Foodborne botulism may be prevented by the inactivation of the bacterium and its spores in heat-sterilized (for example, retorted) or canned products, or by inhibiting bacterial growth and toxin production in other products. The vegetative forms of bacteria can be destroyed by boiling, but the spores can remain viable after boiling even for several hours. However, the spores can be killed by very high temperature treatments such as (commercial) canning.
Commercial heat pasteurization (including vacuum packed pasteurized products and hot smoked products) may not be sufficient to kill all spores and therefore the safety of these products must be based on preventing bacterial growth and toxin production. Refrigeration temperatures combined with salt content and/or acidic conditions will prevent the growth of the bacteria and formation of toxin.
The neurotoxins themselves are heat-labile and will be destroyed within minutes at temperatures above 80°C; consequently, only foods improperly processed in which the bacteria or the spores survive, pose a risk.
The WHO five keys to safer food serve as the basis for educational programmes to train food handlers and educate the consumers. They are especially important in preventing food poisoning.
The five keys are:
- keep clean
- separate raw and cooked
- cook thoroughly
- keep food at safe temperatures
- use safe water and raw materials.
Further information
– FAO/WHO International Food Safety Authorities Network (INFOSAN)
– Santé Publique France. Press conference
– Prefet de la Gironde. Press conference
– ECDC Surveillance Atlas of Infectious Diseases
– European Centre for Disease Prevention and Control. Facts about botulism
– WHO Fact sheets. Food safety
Citable reference: World Health Organization (20 September 2023). Disease Outbreak News; Botulism in France. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON489
