Echovirus 19 Molecular Epidemiology in Russia and Some Central Asian Countries in 1999-2024.

Echovirus 19 (E19) is a rarely reported non-polio enterovirus (NPEV), although it has been associated with a spectrum of severe syndromes, including encephalitis, meningitis, and multisystem hemorrhagic disease in infants. Moreover, Echovirus 19 has been detected in patients with acute flaccid paralysis (AFP), suggesting a potential association between viral infection and CNS damage. Here we describe molecular epidemiology of Echovirus 19 in Russia and Central Asia from 1999 to 2024 using data on poliomyelitis surveillance. Echovirus 19 accounted for no more than 4% of annual NPEV isolates, however, in 2022 abundance rate dramatically increased making this virus the most frequently isolated NPEV from AFP cases (14.3% of NPEV-positive AFP cases). Phylogenetic analysis revealed that contemporary (2020-2025) regional isolates formed a distinct, well-supported clade sharing a common ancestor with Echovirus 19 variants isolated from AFP cases in Iran and Pakistan in 2013. Notably, these recent isolates lack sustained country-specific sublineages indicating ongoing cross-border circulation. A novel A83S mutation in the BC-loop of the VP1 antigenic region was identified in 75% isolates collected in 2022-2025. The emergence of this variant highlights the need for continued surveillance and further investigation into the Echovirus 19 possible role in neurological diseases.