The aetiology and pathogenetic mechanisms of disease are still under investigation. A possible association with current adenovirus infection has been found in cases in the UK in particular but other hypotheses and possible co-factors are under investigation. Most cases continue to be reported as sporadic un-linked cases.
This report presents an update of probable cases identified in the European Union/European Economic Area (EU/EEA) and worldwide. Whereas cases detected in the EU/EEA have been reported according to the ECDC/WHO case definition, worldwide cases are collected through screening of official websites and media sources and therefore different case definitions could have been used.