Infectious Diseases 2025

Public health officials are investigating a multistate outbreak of Salmonella enterica serovar Mbandaka infections associated with contact with backyard poultry. Epidemiologic, traceback, and laboratory data indicate that contact with backyard poultry is contributing to human illness. As of April 24, 2025, a total of seven individuals infected with the outbreak strain of Salmonella Mbandaka have been reported from six U.S. states. Illness onset dates range from February 9 to March 24, 2025.
The actual number of individuals affected is likely higher than the number of reported cases, and the outbreak may extend beyond the states with confirmed cases. This underreporting is attributable to the fact that many infected individuals recover without seeking medical care and are therefore not tested for Salmonella. Among the seven individuals with available animal contact data, five (71%) reported contact with backyard poultry prior to illness onset. Of the four individuals with data on poultry acquisition, two (50%) reported having recently purchased or received poultry, primarily from agricultural retail stores.
The outbreak strain has been previously linked to two hatcheries implicated in past outbreaks. One of these hatcheries is also associated with a poultry shipping material sample collected during the current investigation. Whole genome sequencing (WGS) demonstrated that bacterial isolates from affected individuals are genetically closely related. Investigators in Ohio collected environmental samples from materials used to ship poultry - specifically box liners and bedding - originating from hatcheries and distributed to retail stores. WGS analysis confirmed that the Salmonella Mbandaka recovered from these samples was genetically indistinguishable from the outbreak strain.
Several significant foodborne outbreaks caused by Salmonella enterica serovar Mbandaka have been reported globally in recent years.
In early 2010, Austria experienced a large outbreak of S. Mbandaka associated with table eggs, ultimately traced to contaminated poultry feed. Epidemiological investigation revealed that many affected individuals had consumed raw or undercooked eggs or egg-containing dishes, implicating eggs as the likely vehicle of infection. Active case finding identified 159 confirmed cases nationwide. Environmental sampling of 226 laying hen flocks detected the outbreak strain in two flocks, and S. Mbandaka was also isolated from commercial feed samples obtained from one of the implicated farms [1].
A large cross-border outbreak of S. Mbandaka sequence type ST413 emerged in Europe in late 2021 and continued into 2022. As of November 8, 2022, 196 cases had been reported - 140 confirmed and 56 probable - across at least seven EU/EEA countries (Czechia, Estonia, Finland, France, Germany, Ireland, and the Netherlands), as well as the United Kingdom and Israel. Cases affected individuals across all age groups. Nineteen patients were hospitalized, five developed sepsis, and one elderly individual in the UK died. Epidemiological investigations across multiple countries identified ready-to-eat (RTE) chicken products, distributed through both retail and food service sectors, as the likely source of infection [2].

1. Allerberger F. Molecular typing in public health laboratories: from an academic indulgence to an infection control imperative. Journal of Preventive Medicine and Public Health. 2012 Jan 31;45(1):1.

2. European Centre for Disease Prevention and Control, European Food Safety Authority. Multi‐country outbreak of Salmonella Mbandaka ST413, possibly linked to consumption of chicken meat in the EU/EEA, Israel and the UK. EFSA Supporting Publications. 2022 Dec;19(12):7707E.