Viral meningitis — Rapid | Doctor’s Passport

Synopsis

Differentiate viral meningitis from bacterial, encephalitic and chronic infection, interpret cerebrospinal-fluid PCR with timing and immune status, use antivirals selectively, and stop unnecessary antibiotics only after safe reassessment.

Viral meningitis usually causes fever, headache, neck stiffness, photophobia and nausea while cognition remains relatively preserved.
Enteroviruses are common; HSV-2, varicella zoster, acute HIV, mumps and other viruses are selected by lesions, vaccination, season, exposure and immune status.
Perform lumbar puncture promptly when safe, sending cells, paired glucose, protein, bacterial studies and exposure-directed viral PCR.
Lymphocytic pleocytosis with preserved glucose supports viral meningitis but does not exclude early bacterial, TB, fungal or partially treated infection.
Treat bacterial meningitis empirically until clinical and microbiological evidence supports stopping; stewardship is an active reassessment, not a timetable.
Give intravenous aciclovir for suspected HSV or VZV encephalitis and for severe or high-risk HSV or VZV meningeal disease under specialist guidance.
An isolated positive PCR can represent persistence or contamination; integrate viral target, quantity if available, timing, host and CSF inflammation.
Provide hydration, antiemesis, simple analgesia and return advice, and investigate recurrent aseptic meningitis or persistent neurological symptoms.

Key red flags

Altered behaviour, focal seizure or focal deficit suggests encephalitis rather than isolated meningitis and needs intravenous aciclovir.

Purpura, shock, high lactate or neutrophilic low-glucose CSF requires bacterial treatment despite a plausible viral exposure.

Low CSF glucose, cranial neuropathy or a subacute course raises TB, cryptococcus, malignancy and other chronic meningitis.

Pregnancy, transplantation, advanced HIV or antibody deficiency changes viral spectrum, persistence and treatment threshold.

HSV-2 meningitis

Genital lesions, sacral symptoms or recurrent episodes can accompany HSV-2 lymphocytic meningitis, but lesions may be absent.

VZV meningitis

Dermatomal rash, cranial neuropathy or vasculitic features raises VZV, while zoster sine herpete can occur.

Encephalitic conversion

Confusion, personality change, focal seizure or deficit signifies parenchymal involvement and requires urgent aciclovir and MRI or EEG.

Investigation priorities

Lumbar puncture with broad CSF panelFirst step

Separate bacterial, viral and chronic meningeal patterns and identify a viral target.

Management branches

ASSESSExclude dangerous mimics

A patient presents with a possible aseptic meningitis syndrome.

Stabilise physiology and examine cognition, focal neurology, skin, eyes and immune status before attributing symptoms to a benign virus.
Take blood cultures and perform lumbar puncture promptly when safe; start bacterial treatment whenever danger or CSF uncertainty persists.
Add aciclovir immediately for encephalitic features and request MRI, EEG and repeat HSV testing according to timing.
Investigate low glucose, cranial neuropathy, prolonged course or high opening pressure for TB, cryptococcus, malignancy and inflammatory causes.

Key medicines

Supportive analgesiaGive paracetamol 500 mg to 1 g orally up to four times daily, at least 4 hours apart, maximum 4 g daily in a suitable adult.Reduce maximum for low weight, liver disease, malnutrition or heavy alcohol use and avoid duplicate combination products.

Intravenous aciclovir for severe HSV or VZV diseaseGive aciclovir 10 mg/kg intravenously every 8 hours using protocol weight and renal adjustment when encephalitis or severe high-risk disease is suspected.Hydrate, monitor creatinine and neurological toxicity and never delay treatment for MRI or lumbar puncture when encephalitis is credible.

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