Synopsis
Diagnose aseptic meningitis without prematurely withholding antibacterial treatment, identify viral causes needing targeted therapy or public-health action, and give realistic recovery and safety-net advice.
- Viral meningitis presents with fever, headache, photophobia, neck stiffness, nausea and malaise, usually with preserved or only mildly altered cognition; substantial encephalopathy suggests encephalitis or severe systemic disease.
- Enteroviruses are frequent causes, while herpes simplex virus type 2, varicella-zoster virus, acute HIV, mumps and travel-related arboviruses become relevant in the right exposure context.
- Clinical appearance and cerebrospinal-fluid lymphocytes do not immediately exclude bacterial meningitis, because early viral infection may be neutrophilic and partially treated bacterial disease may become lymphocytic.
Key red flags
Sustained altered behaviour, new focal deficit, dysphasia or seizure signifies brain involvement and requires urgent aciclovir and encephalitis investigation.
Investigation priorities
Preserve evidence of bacterial disease and identify organ dysfunction before treatment.
Management branches
A patient presents with fever, headache and meningism.
- Assess ABCDE, consciousness, rash, focal neurology and seizures, taking blood cultures and urgent blood samples while initiating sepsis support where required.
- Give empirical antibacterial treatment and dexamethasone according to the bacterial-meningitis pathway whenever that diagnosis remains plausible; do not wait for a viral PCR.
The patient is stable and cerebrospinal fluid or PCR supports a viral cause.
Key medicines
ParacetamolUse the current BNF adult oral regimen, reducing the maximum in low body weight, liver disease or other circumstances that increase toxicity risk.
Intravenous aciclovirWhen HSV or VZV encephalitis is possible, use the current BNF weight-based intravenous regimen, commonly 10 mg/kg every 8 hours, with renal adjustment and specialist oversight.