Enterovirus D68 and A71 recognized by the Acute Flaccid Paralyses (AFP) Surveillance in Northern Italy in 2016

Acute Flaccid Paralyses Surveillance (AFPS) is the strategic system to monitor the emergence of polioviruses (wild and vaccine-derived) in polio-free countries and it is a sensitive case-based scheme to recognize non-polio enteroviruses (NPEVs). We report the findings of AFPS activities in Lombardy (Northern Italy) during 2016 in the framework of the Italian nationwide AFPS. Methods Physicians enrolled children <15 years who met the WHO definition of AFP case. Clinical samples were collected for virological investigations and analysed by virus isolation in RD and L20B cell cultures, and by RTPCR assay specific for the 5′ noncoding region (nt. 179-575) of EVs. EVpositive specimens were further analysed by sequencing a fragment of the EV-VP1 (nt. 2602-2977) gene. Results In 2016, 15 AFP cases were reported in Lombardy with an incidence of 1.07/100’000 children <15 years. The median age of AFP cases was 3.6 years [inter-quartile range (IQR): 4.8 years]; 93% of cases were males. No polioviruses were identified and NPEVs were detected in 20% (3/15) of AFP cases. Molecular characterization and phylogenetic analysis of NPEVs showed the presence of one Echovirus-25, one EVD68 (similarity >98.6% with sequences of B3 lineage identified in the 2016 Dutch outbreak) and EV-A71 (similarity >98.4% with sequences of subgenogroup C1 detected in the 2015 German epidemic). Conclusion The results of 2016 AFPS confirmed the absence of poliovirus in the surveyed area, and provided valuable and up-to-date information on the occurrence of NPEVs of public health concern in Northern Italy. The unpredicted detection of EV-D68 and EV-A71, sharing high nucleotide similarity with viruses involved in the latest European outbreaks, emphasises the importance of monitoring NPEVs through AFPS to help public health response.