Enterovirus- en parechovirus-surveillance in Nederland, 2015-2021

Abstract

Enteroviruses (EVs) and parechoviruses (PEVs) circulate worldwide and can cause a wide variety of symptoms. The clinical EV/PEV surveillance is primarily aimed at excluding/confirming poliovirus (PV) in fecal samples tested positive for EV, and secondary at monitoring non-polio enteroviruses (NPEVs) and PEVs in all EV- and PEV-positive samples. With the recent increase in severity of NPEVs and PEVs, monitoring of NPEV and PEV circulation has become more important in the clinic and public health setting. The aim of this study is to describe the epidemiological and virological characteristics of NPEV and PEV circulation and to investigate the adequacy of PV exclusion. The surveillance is a collaboration between RIVM and a national network of medical microbiological laboratories that perform EV/PEV diagnostics/typing (n=36). Data on EV/PEV diagnostics and typing from 2015-2021 have been analyzed and show the yearly and monthly/seasonal detection and circulation of PV, NPEVs and PEVs and the different circulating types. The number of samples tested has increased over the years. An average of 28,740 (EV) and 18,718 (PEV) samples was tested per year. The percentage of positive samples fluctuated between 5-9% (EV) and between 1.5-3.5% (PEV). The SARS-CoV-2 pandemic and COVID-19 measures have led to a lower circulation of NPEVs and PEVs was observed, particularly in 2020. Most EV and PEV positive samples were mainly detected in the summer spurring on into autumn/early winter. However, in 2020 and 2021 the detection in the fall/early winter was higher than in the summer. The NPEV types CV-A6, CV-B5, E-6, E-11, E-25, and EV-D68, and PEV types PEV-A1 and PEV-A3 were frequently found in the study period. Based on the data analyzed, the percentage of EV-positive fecal samples that have been typed is about 60-70% and decreases over the years studied. However, the percentage of EV-positive fecal samples in which PV was excluded was lower and is about 50-60%. This is because culture on PV-permissive cells (L20B cells) was performed only in a small part of those EV positive fecal samples where no NPEV type could be identified. Typing of EV and PEV positive samples is essential to monitor the epidemiological and virological features of NPEV and PEV circulation and PV detection. These data, and if possible combined with clinical data, are needed for early detection and outbreak investigation of NPEVs and for the purpose of monitoring potential public health threats