Letter to the Editor: Dengue virus as an underrecognized cause of encephalitis in tropical Asia - Bridging diagnostic and surveillance gaps.

Arboviral encephalitis remains a major public health concern in tropical Asia, where the etiology of a substantial proportion of central nervous system infections remains undetermined despite endemic circulation of dengue virus (DENV) and Japanese encephalitis virus. Laboratory confirmation is frequently absent in clinically suspected encephalitis. Perera et al recently published a study in World Journal of Virology, highlight this diagnostic gap by identifying DENV infection in 6.06% of encephalitis cases, including molecular evidence of DENV-3 neuroinvasion. These findings add to the growing evidence that DENV can cause encephalitis and meningoencephalitis across age groups. However, encephalitis in endemic settings is etiologically heterogeneous, and dengue represents only one of several infectious and immune-mediated contributors. Neurological dengue is likely under-recognized due to overlapping clinical presentations and limited diagnostic capacity. The identification of DENV-3 is noteworthy given its recurrent association with neurological disease. Limited concordance between reverse transcription polymerase chain reaction and immunoglobulin M assays reflects challenges related to viral kinetics, timing of specimen collection, and flaviviral serological cross-reactivity. Strengthening surveillance through integrated molecular and serological diagnostic strategies, including multiplex polymerase chain reaction and metagenomic next-generation sequencing, is essential to reduce undiagnosed encephalitis and improve clinical management and public health preparedness in tropical Asia.