An uncommon cause of tinea: Trichophyton violaceum in a German kindergarten – outbreak report and quantitative analysis of epidemiological data from Europe

Background: Global mobility is increasingly associated with the emergence of “unusual” infectious agents. At the beginning of 2019, a putative outbreak of Impetigo contagiosa occurred in a kindergarten in Regensburg, Germany, that was mainly attended by children with a migrant background. After thorough examination, the outbreak was classified as infection with Trichophyton (T.) violaceum. Methods: Based on case investigations, infection control measures, disinfection, and cleaning were implemented. Microscopy of native specimens, fungal cultures, and polymerase chain reaction were used for diagnosis. Additionally, a systematic literature search in Medline, followed by a quantitative analysis of epidemiological data from Europe, were performed. Results: Between January and November 2019, 12 cases of tinea were diagnosed in 7 educators and 2 household members. Children were initially not affected. T. violaceum was only detected in 2 patients. No extensive screening measures were carried out after risk-benefit assessment. Studies on T. violaceum in Europe are heterogeneous, and the number of cases and the prevalence vary considerably. The pathogen is mainly found in children of African descent who clinically present with tinea capitis. Discussion: In the present case, the source of infection and the chain of transmission remained unclear. The pathogen could only be diagnosed in 2 cases. In Europe, the (re)emergence of pathogens such as T. violaceum is likely to be caused by increasing migration and travel. Pathogens should be identified for epidemiological reasons in all cases. In outbreaks, measures must be adapted to the dynamics of the individual outbreak after assessment of the risks, benefits, and proportionality.