Enhanced genomic surveillance of enteroviruses reveals a surge in enterovirus D68 cases, the Johns Hopkins health system, Maryland, 2024.

This study reports increased Enterovirus D68 (EV-D68) circulation in 2024, re-establishing its biennial circulation cycle after its interruption during the COVID-19 pandemic. A total of 1,395 respiratory and cerebrospinal fluid (CSF) samples, positive for rhinovirus/enterovirus, collected from January to November 2024 were screened. EV-D68 was the predominant enterovirus detected (72.6% of EV-positive samples), with cases peaking in October, consistent with historical seasonal patterns. Demographically, children under 5 years were predominantly infected with EV-D68 (41.6% of cases). Phylogenetic analysis revealed the co-circulation of two EV-D68 subclades: B3 (71%) and A2 (29%). Subclade B3 was primarily associated with pediatric infections (median age: 5 years), while A2 was more common in adults (median age: 42 years). Comparative genomic analysis of the 2024 B3 genomes, along with genomes from 2018 and 2022, identified the emergence of four amino acid substitutions, including three in nonstructural proteins (3C: I597V; 3D: I950V, T2173A) and one in the structural protein VP2 (T145S). The six positive enterovirus CSF samples diagnosed in 2024 included six different types: EV-D68, E9, E30, E18, CV-A9, and CV-B1. Notably, the 2024 EV-D68 outbreak did not coincide with a reported increase in acute flaccid myelitis (AFM) cases. This study highlights the importance of EV-D68 genomic surveillance for monitoring EV-D68 evolution, given its association with severe respiratory disease and neurological complications. Enhanced surveillance is also critical for the early detection of the emergence of enteroviruses, such as EV-C105, identified in this study.IMPORTANCEEnteroviruses (EVs), a genus within the