The role of Shiga toxin-producing Escherichia coli (STEC) in outbreaks of food-borne illnesses is well recognised [1]. According to surveillance studies, STEC of serotype O157:H7 are those most often associated with epidemics of STEC infections worldwide [2–4] and most likely to cause severe infections with systemic complications such as haemolytic uremic syndrome (HUS) [5]. Nonetheless, STEC belonging to non-O157 serogroups raised public health concern in many countries by displaying the same pathogenic potential as O157:H7 [6–8]. Among them, STEC O26 poses a significant threat to human health in terms of illness severity and the risk of causing outbreaks. This serogroup is considered emerging in Europe and in the last decade, it was reported as the most frequent non-O157 STEC serogroup in human sporadic cases of infection, including those developing HUS [9]. Severe outbreaks of STEC O26 infection have been reported both in community [6] and childcare settings [10]. In 2013, the emergence of a highly virulent clone of STEC O26 strongly associated with HUS in Europe was described in the scientific literature [11].
At the beginning of 2016, Romania alerted the European Centre for Disease Prevention and Control (ECDC) of an unprecedented rise in haemolytic uremic syndrome (HUS) cases in the paediatric population. It reported on 15 children aged between 5 and 38 months who were diagnosed with HUS, some of whom progressed to HUS after bloody or non-bloody diarrhoea. Cases were linked to STEC O26 infection by serology and most resided in one of the southern districts [12]. Food consumption history of cases suggested that dairy products from a local producer were among the foodstuff potentially implicated in the outbreak as the source or vehicle of infection, but this suspicion was not confirmed microbiologically. Soon after the description of the first cases in Romania, Italy reported one HUS case with epidemiological link to Romania through the Early Warning and Response System (EWRS) of the European Union, suggesting that a multi-country outbreak of STEC infections was ongoing [13].
