Aseptic (Viral) Meningitis — Diagnosis and Management

Aseptic meningitis denotes meningeal inflammation in the absence of identifiable bacterial pathogens on routine cultures. Although viral etiologies predominate (giving rise to the synonym 'viral meningitis'), the term technically encompasses non-infectious causes (drug-induced, autoimmune, neoplastic) and partially treated bacterial meningitis. Annual incidence in the United States exceeds 75,000 cases, with seasonal peaks in summer and early autumn reflecting enteroviral epidemiology.

Enteroviruses (coxsackievirus A and B, echoviruses, enterovirus 71, parechoviruses) cause 85-90% of viral meningitis cases, transmitted primarily through fecal-oral and respiratory routes. Herpes simplex virus type 2 accounts for benign recurrent lymphocytic meningitis (Mollaret meningitis), while HSV-1 typically causes encephalitis rather than isolated meningitis. Other significant pathogens include varicella-zoster virus, mumps virus (declining with vaccination), HIV (acute seroconversion syndrome), arboviruses (West Nile, Zika, La Crosse, eastern/western equine encephalitis), and rarely lymphocytic choriomeningitis virus.

Clinical presentation typically includes acute headache, fever, photophobia, neck stiffness, and constitutional symptoms developing over hours to days, generally less severe than bacterial meningitis. Cerebrospinal fluid analysis reveals lymphocytic pleocytosis (typically 50-1000 cells/mm³), mildly elevated protein (usually <150 mg/dL), and normal glucose ratio (CSF/serum >0.6). Multiplex PCR for enteroviruses, HSV, VZV, and other pathogens has revolutionized rapid etiologic diagnosis. Bacterial meningitis must be excluded based on clinical suspicion, CSF parameters, and rapid antigen or PCR testing.