Forgotten but not gone: Yersinia infections in England, 1975 to 2020

Background: Yersiniosis is one of the most common food-borne zoonoses in Europe, but there are large variations in the reported incidence between different countries. Aim: We aimed to describe the trends and epidemiology of laboratory-confirmed Yersinia infections in England and estimate the average annual number of undiagnosed Yersinia enterocolitica cases, accounting for under-ascertainment. Methods: We analysed national surveillance data on Yersinia cases reported by laboratories in England between 1975 and 2020 and enhanced surveillance questionnaires from patients diagnosed in a laboratory that has implemented routine Yersinia testing of diarrhoeic samples since 2016. Results: The highest incidence of Yersinia infections in England (1.4 cases per 100,000 population) was recorded in 1988 and 1989, with Y. enterocolitica being the predominant species. The reported incidence of Yersinia infections declined during the 1990s and remained low until 2016. Following introduction of commercial PCR at a single laboratory in the South East, the annual incidence increased markedly (13.6 cases per 100,000 population in the catchment area between 2017 and 2020). There were notable changes in age and seasonal distribution of cases over time. The majority of infections were not linked to foreign travel and one in five patients was admitted to hospital. We estimate that around 7,500 Y. enterocolitica infections may be undiagnosed in England annually. Conclusions: Findings suggest a considerable number of undiagnosed yersiniosis cases in England, with possibly important changes in the epidemiology. The apparently low incidence of yersiniosis in England is probably due to limited laboratory testing.