Researchers have looked into the number of and factors behind Salmonella outbreaks linked to chocolate products in recent decades.

No predominant Salmonella serotype was identified, according to the Pediatric Infectious Disease Journal study.

Researchers performed a systematic review of three databases. Eligible articles were published after 1970, describing outbreaks of more than ten patients with non-typhoidal salmonellosis associated with consuming chocolate food products.

Twenty-three articles published between 1972 and 2022 were part of the final analysis. They described 12 Salmonella outbreaks linked to chocolate consumption. 

Examples of outbreaks
A dozen outbreaks involved 3,266 patients. Two occurred in the 1970s, three in the 1980s, one in the 1990s, three from 2000 to 2009, and three afterward. Six outbreaks peaked in winter, three in autumn, two in spring, and one in summer.

Six outbreaks involved one country, and five involved two or more countries. On three occasions, the outbreak spread across two continents.

In 2022, a large outbreak of monophasic Salmonella typhimurium linked to chocolate products from a Ferrero factory in Belgium affected more than 450 patients in 16 countries.

From 2018 to 2019, 85 people fell sick in Canada with Salmonella Enteritidis in chocolate French pastries. Also, in 2018, Salmonella Thompson affected 1,111 people who ate chocolate cake in South Korea.

The number of cases in each outbreak ranged from 29 to 1,111. For studies wher the median age was provided, it ranged from 3 to 15 years old. The hospitalization rate varied between 3 percent and 41 percent.

Seasonal impact
Chocolate is an optimal medium for the spread of Salmonella. This is because the low water content and high-fat level increase the thermal resistance of the pathogen. Higher temperatures during chocolate production, despite eliminating Salmonella, would worsen its taste, plus the pathogen may persist for more than one year in chocolate, said researchers.

Salmonellosis outbreaks typically occur during warmer months. However, most outbreaks associated with chocolate were in the cold season. Researchers said popular seasonal products such as chocolate Santa Clauses and Easter bunnies might be the reason for this finding.

Potential explanations for children being mainly affected include this group being more susceptible to intestinal infections, person-to-person transmission being more common due to behaviors that increase germ exposure, and chocolate’s appeal to this demographic.   

All reported outbreaks were in high-income countries.

“This finding may be related, on the one hand, to the large availability of industrially produced food and, on the other hand, to the presence of effective outbreak detection and control networks in these countries. It is also conceivable that outbreaks detected in middle-income and low-income countries have not been reported. A connected worldwide reporting system including high-income, middle-income, and low-income countries is crucial to detect infectious disease outbreaks in an early phase and avoid their spread,” said scientists.