Enterovirus-D68 (EV-D68) in pediatric patients with respiratory infection: The circulation of a new B3 clade in Italy

BACKGROUND: In recent years, several outbreaks due to Enterovirus D-68 (EV-D68) have been reported, and it was confirmed that the virus can cause upper and lower respiratory tract diseases and be associated with the development of neurological problems. OBJECTIVES: The main aim of this research was to study the genetic characteristics of EV-D68 strains that were circulating in Italy identified during an outbreak of an EV-D68 infection that occurred in Italy during the period March-October 2016. STUDY DESIGN: A retrospective study of the circulation of different types and subtypes of EV-D68 was performed. Nasopharyngeal swabs were collected from March 2016 through October 2016 in children admitted to the Emergency Room with respiratory diseases. RESULTS: Among 390 children, 22 (59.1% males; mean age 47 months) were found to be infected by EV-D68 and most of them were immunocompetent (72.7%). Pneumonia was diagnosed in 12 (54.5%) children. Phylogenetic analysis of the VP1 region showed that all the strains identified in this study belonged to clade B3. Within B3 subclade, the Italian EV-D68 strains were most closely related to strains detected in Southern China in 2015 as well as to strains detected in US and the Netherlands in 2016. CONCLUSIONS: These results showed that EV-D68 infections are a common cause of lower respiratory illness in pediatric age. The circulation of one EV-D68 lineage has been proven in Italy and in the European region during 2016. However, further studies are required to investigate whether some strains or lineages may possess a higher affinity for the lower airway or central nervous system.