Rapid outbreak assessment – first update: Multi-country Salmonella outbreak linked to chocolate products
On 18 May 2022, ECDC and EFSA published an update of the rapid outbreak assessment on a multi-country outbreak of monophasic Salmonella Typhimurium linked to chocolate products made at a factory in Arlon, Belgium.
As of 18 May 2022, 324 cases (266 confirmed and 58 probable) have been reported in the EU/EEA (Austria, Belgium, Denmark, France, Germany, Ireland, Italy, Luxembourg, Netherlands, Norway, Spain, Sweden) and the UK, including two distinct strains of monophasic S. Typhimurium. In addition, cases have been identified in Canada, Switzerland, and the United States.
Most infections (86.3%) are among children at or younger than 10 years old, and for all cases in the EU/EEA and the UK with information available, 41.3% of them have been hospitalised. No deaths were reported.
The two Salmonella strains are multidrug-resistant, and some tested isolates also carry resistance to disinfectants that are based on quaternary ammonium compounds and hydrogen peroxide, but remain susceptible to azithromycin, ciprofloxacin, meropenem, and third generation cephalosporins. Epidemiological and microbiological investigations have identified specific chocolate products manufactured in the processing Plant in Arlon, Belgium, as likely vehicles of infection.
The two outbreak strains of monophasic S. Typhimurium were identified in ten of 81 Salmonella positive samples taken in the plant between December 2021 and January 2022, including raw material (buttermilk), semi-finished and finished products. The buttermilk was provided by an Italian supplier where Salmonella was not detected. The Italian supplier has delivered the buttermilk also to other production plants of the company and based on the available evidence, Salmonella has not been detected in other plants.
The closure of the Belgian processing plant on 8 April 2022 and the global recall and withdrawal of all their products have reduced the risk of exposure, but new cases may occur due to the long shelf life and possible storage of products at home.
The public health impact of the rigorous control measures implemented can be reflected in the significant drop of reported cases between weeks 14 and 15 in April 2022. However, among 156 cases reported in this outbreak with available dates, the median delay between disease onset and notification to the national surveillance system was three weeks with a maximum of five weeks. It is also likely that cases in countries that have not reported cases may have remained undetected if cases were not sequenced routinely.
Finally, there are eight cases, which cannot be explained by consumption of chocolate products from the same processing plant in Belgium, suggesting that there may also be other sources of infection, albeit secondary infections, which cannot be excluded.
ECDC continues to monitor the situation and encourages Member States to be alert for new cases and investigate human infections with strains that have multi-drug resistance profiles. Further sequencing of such isolates is recommended, and ECDC offers sequencing support for countries with limited or no genome-sequencing capacity.
In addition, ECDC further encourages public health authorities to cooperate closely with food safety authorities in the countries affected.
Following the detections of Salmonella in buttermilk, semi-finished and finished products, the company implemented hygiene control measures and increased sampling and testing of the products and the processing environment. Batches of products were released to the market after negative results of Salmonella testing. The chocolate products have been distributed across Europe and globally.
In the beginning of April 2022, upon availability of sequencing data, scientists linked human cases to Belgian chocolate factory through advanced molecular typing techniques.
Since 2 April 2022, national competent authorities have begun to issue public health warnings. On 8 April 2022, the food safety authority in Belgium performed official controls at the factory and withdrew the company’s authorisation for production. In addition, the company initiated recalls of all batches of products produced at the Arlon factory, regardless of their lot number or expiration date.