Hemolytic-uremic syndrome in children in Norway: a study on epidemiology, surveillance, clinical aspects and outcome

Abstract

Hemolytic-uremic syndrome (HUS) is a severe clinical syndrome defined by impaired renal function, hemolytic anemia and thrombocytopenia. It mainly affects children of pre-school age, and is one of the most common causes of pediatric acute kidney injury (AKI) in Europe. HUS can be classified by clinical presentation as diarrhea-associated (D+HUS) or not (D-HUS). D+HUS constitute around 90 % of cases and is primarily caused by infection with Shiga toxin-producing Escherichia coli (STEC). Both conditions are under epidemiological surveillance in Norway. The first national Norwegian outbreak of STEC-related HUS occurred in 2006; ten children developed HUS, one with a fatal outcome. This brought HUS to national public attention and led to mandatory notification of all D+HUS to the Norwegian Surveillance System for Communicable Disease (MSIS). The aims of this thesis was to examine central aspects of HUS in children in Norway, focusing on the areas of epidemiology, surveillance, clinical presentation, and outcome, expanded to include surveillance of STEC and epidemiology of pediatric AKI. Data was gathered through a retrospective review of medical records (1999-2008) and cases notified to MSIS (2007-2017). The main findings indicate an underestimating of pediatric HUS occurrence in Norway prior to 2006, but a lower incidence rate compared to other countries. The data also suggest general underreporting of STEC. This is further reinforced by a stable notification rate of HUS and increased rate of “low-virulent” (non-HUS-associated) STEC cases that was linked to implementation of novel STEC identification methods. A high rate and variation of complications in HUS cases is shown. HUS was the second most common cause of AKI in the pediatric population. Overall, these findings emphasize the importance of mandatory notification, surveillance and tailored control measures for both HUS and STEC, and may contribute to the general understanding of HUS.