Meningitis, Viral

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Basics

Description

  • A clinical syndrome characterized by signs/symptoms of acute meningeal inflammation from a viral etiology
  • Viral meningitis (VM) is the most common cause of aseptic meningitis (no identifiable bacterial pathogen in CSF).
  • System(s) affected: nervous

Epidemiology

Incidence
  • Estimated 30,000 to 75,000 VM cases and 26,000 to 42,000 VM hospitalizations annually in United States
  • Most common form of infectious meningitis
    • The annual incidence of VM is higher than all other causes of meningitis combined.
  • Peaks June 1 to October 31
    • Nonpolio enteroviruses and arthropod-borne viruses predominate in warm months (70% of cases July to October).
    • Mumps usually occurs in the winter and spring, often in epidemics; rare due to MMR vaccination

Etiology and Pathophysiology

  • In immunocompetent hosts, VM is generally caused by virus with neurotropic predilection.
  • Less commonly, direct neural transmission occurs from an acute flare of a chronic viral illness (such as HSV) already present in an immunocompetent host.
  • 85–95% of VM cases are caused by enterovirus family (often transmitted by the fecal–oral route), including coxsackievirus A and B, echovirus, and nonpolio E variants: E9 and E30.
  • Less common: HSV-1, HSV-2, varicella-zoster virus (VZV), adenovirus, lymphocytic choriomeningitis virus (LCMV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), HIV, parvovirus B19, mumps, Toscana virus
  • Parechovirus 3 is the most common cause of VM in infants <90 days old.
  • Arthropod-borne viruses: West Nile virus, St. Louis encephalitis virus, California encephalitis virus
  • Recurrent benign lymphocytic (Mollaret) meningitis is 80% associated with HSV-2.

Genetics
None identified

Risk Factors

  • Close contact with known cases of VM
  • Age (common in children <5 years)
  • Immunocompromised host (more susceptible to CMV, HSV, and adenovirus)

Geriatric Considerations
Cases of VM in the elderly are rare (most common cause is VZV, HSV); consider alternative diagnoses (e.g., carcinomatous meningitis, medication-induced aseptic meningitis).

General Prevention

Limit exposure to known hosts; hand washing and general hygiene procedures

Commonly Associated Conditions

Encephalitis; neurologic deficits; myopericarditis; neonatal enteroviral sepsis

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