2635. Outbreak of Enterovirus D68 Among Children in Japan and Simultaneous Circulation of Clade B3 in Europe

BACKGROUND: Enterovirus D68 (EV-D68) is a re-emerging, high-morbidity pathogen that causes severe respiratory infection and acute flaccid myelitis in children. EV-D68 is phylogenetically divided into 4 major groups—clade A through D—and each clade has subclades defined by genetic variant. Outbreaks of all strains have been reported in more than 10 countries. However, no study has compared the viral genomic characteristics of EV-D68 in contemporaneous outbreaks in different countries. METHODS: An outbreak of EV-D68 in children younger than 15 years occurred in Niigata, Japan, from October through November 2018. The patients were admitted to hospital with respiratory distress and wheezing episodes. RNA extracted from nasopharyngeal samples was tested by EV-D68-specific PCR. Clade was determined by semi-nested PCR analysis of the VP1 region, and the phylogenetic tree of the VP1 sequence was constructed. To clarify viral genomic characteristics, we compared the clade to those of outbreaks occurring during 2014–2018 in other countries. RESULTS: EV-D68 testing of 47 patients yielded positive results for 22 (47%) (median age 4.6 years; IQR, 2.9–6.7), and 15 (69%) had a past medical history of allergic disease. No patient developed acute flaccid myelitis. The VP1 sequences from all isolates belonged to clade B3, the same clade detected during the 2015 outbreak in Japan (figure). Interestingly, EV-D68 outbreaks were reported in France and Italy (clades D1/B3 and D1, respectively) during this period. Although the EV-D68 clades responsible for outbreaks in 2014 differed by region, clade B3 is now the dominant clade and has caused concurrent EV-D68 outbreaks in children since 2015 (table). CONCLUSION: In 2018, an EV-D68 clade B3 outbreak occurred among children in Niigata, Japan. This clade is now dominant and periodically circulates around the world. Because EV-D68 can cause simultaneous outbreaks worldwide and is associated with high morbidity, detailed real-time epidemiological surveillance of EV-D68 is warranted. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.