A 4-month-old infant presented with fever, irritability, poor feeding, and a bulging fontanelle, initially suspected of bacterial meningoencephalitis. Cerebrospinal fluid analysis revealed pleocytosis and elevated protein. Despite initial antibiotic treatment, the infant's condition worsened. Subsequent metagenomic next-generation sequencing (mNGS) of CSF identified Eastern equine encephalitis virus (EEEV) as the causative agent, leading to a diagnosis of EEEV meningoencephalitis. This case highlights the critical role of advanced diagnostic techniques like mNGS in identifying rare or unexpected pathogens, especially in severe neurological infections where conventional methods fail.
Key note: Metagenomic next-generation sequencing is invaluable for diagnosing atypical meningoencephalitis.