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BASICS

Viral meningitis (VM) is a clinical syndrome with fever and signs of acute meningeal inflammation (headache, photophobia, neck stiffness, nausea/vomiting). It is the most common cause of aseptic (nonbacterial) meningitis.

EPIDEMIOLOGY

  • Most common form of meningitis
  • Peaks in summer to fall in temperate climates; year-round in tropical/subtropical
  • Nonpolio enteroviruses cause ~75,000 cases annually in the U.S.
  • Prevalence varies by geography and virus

ETIOLOGY AND PATHOPHYSIOLOGY

  • Common viruses in immunocompetent: gastroenteritis viruses, mumps, HSV, VZV, arboviruses
  • Emerging reports: SARS-CoV-2, rotavirus A, hepatitis E
  • Immunocompromised: CMV, EBV
  • 23-61% cases caused by nonpolio human enteroviruses via fecal-oral route
  • Mosquito-borne: West Nile, Zika, chikungunya, dengue, St. Louis encephalitis, Eastern equine encephalitis
  • Tick-borne: Powassan, Colorado tick fever, tick-borne encephalitis viruses
  • Recurrent Mollaret meningitis: mainly HSV-2 (80% of cases)
  • No identified genetics

RISK FACTORS

  • Age: most common in children <5 years
  • Babies <1 month: more severe disease
  • Immunocompromised: susceptibility to CMV, HSV, EBV
  • Diabetes, chronic renal failure: susceptibility to VZV
  • Close contacts unlikely to get VM, but may get primary viral syndrome
  • Elderly VM rare; consider alternative diagnoses (cancer, drug-induced aseptic meningitis)

GENERAL PREVENTION

  • Hand hygiene
  • Avoid sharing drinks/cups/silverware with ill individuals
  • Protect against mosquitos and ticks (clothing, DEET, nets)
  • Keep immunizations updated

COMMONLY ASSOCIATED CONDITIONS

  • Encephalitis
  • Myopericarditis
  • Neonatal enteroviral sepsis
  • Meningoencephalitis
  • Flaccid paralysis

DIAGNOSIS

HISTORY

  • Adults: acute onset (hours-days)
  • Fever (varies by virus: 65-83% enterovirus, 54-98% mumps, 6-52% HSV)
  • Headache (early), photophobia (enterovirus 79-85%, HSV 33-64%, mumps 7%)
  • Myalgias/arthralgias (enterovirus 88%, HSV 50%, mumps 14-21%)
  • Nausea/vomiting, malaise
  • Nuchal rigidity (enterovirus 55-69%, HSV 22-71%, mumps 8-85%)
  • Altered mental status, seizures, focal deficits → consider alternate diagnoses
  • Infants: nonspecific (poor feeding, vomiting, lethargy, fever, irritability)
  • Additional: travel, sexual history, immunocompromised status, prior infections, immunizations

PHYSICAL EXAM

  • Vital signs: fever, tachycardia, tachypnea, hypotension
  • Neuro: lack of mental status changes (if present, consider alternatives), photophobia, meningeal signs
  • Nuchal rigidity, Brudzinski, Kernig signs have poor sensitivity (~5%)
  • Jolt accentuation test: questionable utility【2】
  • Asymmetric flaccid paralysis in West Nile virus【1】
  • HEENT: parotitis (mumps), herpangina (coxsackievirus A), bulging fontanelle (infants), lymphadenopathy (EBV, HIV)
  • Dermatology: vesicular rash (hand, foot, mouth disease), generalized maculopapular rash
  • Petechial/purpuric rash → consider bacterial meningitis
  • Abdomen: splenomegaly (EBV), abdominal pain

DIFFERENTIAL DIAGNOSIS

  • Bacterial meningitis, fungal meningitis (immunocompromised: Coccidioides, Cryptococcus)【3】
  • Tuberculosis, syphilis, leptospirosis, Lyme disease, ehrlichiosis, amebiasis【3】
  • Parameningeal infections (subdural empyema), encephalitis, postinfectious encephalomyelitis
  • Viral syndrome (influenza)
  • Leukemia, lymphoma, neoplastic disease (metastasis)
  • Migraine, tension headache, metabolic encephalopathy, postoperative aseptic meningitis
  • Drug-induced meningitis (NSAIDs, TMP/SMX, amoxicillin, TNF-α inhibitors, lamotrigine, IVIG, monoclonal antibodies)【1】
  • Brain/epidural abscess, inflammatory disorders (Behçet, sarcoidosis, SLE)【1】

DIAGNOSTIC TESTS & INTERPRETATION

Initial Tests

  • Serum: CBC, BMP, procalcitonin/CRP, blood cultures【3】
  • CBC: normal or mild leukocytosis
  • BMP: CSF glucose compared with plasma
  • Procalcitonin/CRP: normal in VM (elevated suggests bacterial meningitis)
  • Blood cultures: negative in VM
  • Lumbar puncture (LP): differentiates VM from BM
  • Use clinical decision tools (e.g., Bacterial Meningitis Score) to assess BM risk in children
  • Contraindications to LP: increased ICP signs, impaired immunity, local infection, epidural abscess suspicion, anticoagulation
  • CT scan if ICP suspected
  • Risks of LP: herniation, headache, bleeding, infection, pain
  • CSF analysis:
  • Opening pressure: normal
  • WBC 100-1000/µL (may be higher in enteroviral meningitis)
  • Lymphocytic predominance (early infection may show PMNs)
  • RBCs: traumatic tap or HSV meningitis/encephalitis
  • Glucose: normal (may be mildly low in mumps, HIV)
  • Protein: normal to mildly elevated
  • Lactate: normal (<4.2 mmol/L; >4.2 suggests bacterial meningitis or other severe CNS conditions)
  • Gram stain: negative
  • CSF culture: gold standard for bacterial meningitis (negative in VM)
  • PCR/NAAT: improved sensitivity/specificity; rapid identification of pathogens【3】
  • CSF IgM for arboviruses【4】

Follow-Up Tests

  • Consider diabetes, neurologic diseases affecting results

TREATMENT

GENERAL MEASURES

  • Supportive care: pain control, IV fluids
  • Low threshold for empiric antibiotics pending labs (rule out bacterial meningitis)【2】

MEDICATION

  • Antipyretics/analgesics:
  • Acetaminophen 500-1000 mg PO q8h (max 3g/day)
  • Ibuprofen 400-800 mg PO q8h
  • Naproxen 550 mg PO BID
  • Short-term opioids if needed
  • Antiemetics:
  • Ondansetron 4-8 mg IV q8h
  • Promethazine 12.5-25 mg PO/PR/IM/IV q4-6h (max 50 mg/24h)
  • Antivirals:
  • Empiric acyclovir 10 mg/kg IV q8h for suspected HSV meningitis pending PCR
  • Immunocompetent patients often recover without antivirals
  • Antibiotics:
  • Not indicated for VM
  • Empiric antibiotics reasonable if bacterial meningitis cannot be excluded
  • Corticosteroids: not recommended in VM【2】

ISSUES FOR REFERRAL

  • Emergent neurosurgical referral for patients with CSF shunts, recent neurosurgery/trauma, or intrathecal pumps suspected of VM/BM【3】

ADMISSION, INPATIENT, AND NURSING CONSIDERATIONS

  • Initial inpatient management: pain control, empiric therapies, IV fluids, neuro monitoring
  • Contact precautions until bacterial meningitis excluded
  • Discharge based on hydration, pain, function, social support
  • Stable VM patients may be managed outpatient

ONGOING CARE

FOLLOW-UP

  • Ensure symptom resolution
  • Neuropsychological sequelae (cognitive dysfunction, sleep disturbance, psychomotor slowing) possible
  • Developmental surveillance in children

PATIENT MONITORING

  • Watch for relapse or neurologic complications (seizures, altered mental status, weakness)
  • Ensure companion for monitoring after discharge

DIET

  • Push fluids
  • Diet as tolerated

PATIENT EDUCATION

  • Very low transmission risk to contacts
  • Encourage hand washing
  • Symptoms like headache, myalgia, weakness may recur over 2-3 weeks

PROGNOSIS

  • Recovery in 7-10 days generally
  • Some may have delayed return to work, intermittent symptoms lasting weeks to months
  • Low mortality
  • Very young children and some adults may have prolonged neuropsychological effects

COMPLICATIONS

  • Common: fatigue, irritability, muscle weakness
  • Rare: neuropsychological problems, developmental delay

REFERENCES

  1. Shahan B, Choi EY, Nieves G. Cerebrospinal fluid analysis. Am Fam Physician. 2021;103(7):422-428.
  2. Kohil A, Jemmieh S, Smatti MK, et al. Viral meningitis: an overview. Arch Virol. 2021;166(2):335-345.
  3. Poplin V, Boulware DR, Bahr NC. Methods for rapid diagnosis of meningitis etiology in adults. Biomark Med. 2020;14(6):459-479.
  4. Hudson JA, Broad J, Martin NG, et al. Outcomes beyond hospital discharge in infants and children with viral meningitis: a systematic review. Rev Med Virol. 2020;30(2):e2083.

ICD10 Codes

  • A87.9 Viral meningitis, unspecified
  • A87.1 Adenoviral meningitis
  • A87.0 Enteroviral meningitis

Clinical Pearls

  • VM cannot be reliably distinguished from bacterial meningitis based on clinical findings alone.
  • Hospitalize suspected meningitis cases for evaluation and empiric antibiotics until bacterial meningitis ruled out.
  • VM is more common than bacterial meningitis, especially with high vaccination rates.
  • Morbidity and mortality with VM are low.