Synopsis
Recognise mucocutaneous and invasive herpes simplex, start time-critical encephalitis and neonatal therapy, protect the eye, and tailor antiviral dose to site and host.
- HSV-1 commonly causes orolabial, ocular and encephalitic disease; HSV-2 commonly causes genital, neonatal and meningitic disease, but either type can occur at either site.
- Painful grouped vesicles become shallow erosions, while prodromal tingling and recurrent lesions in the same region reflect ganglionic latency and reactivation.
- Confirm atypical mucocutaneous disease with PCR from a freshly unroofed lesion base; serology cannot prove that a current lesion is herpetic.
- For suspected encephalitis, send CSF HSV PCR and obtain MRI, but start intravenous aciclovir within six hours when results are unavailable or the patient is very unwell.
- Give intravenous aciclovir 10 mg/kg every eight hours for adult HSV encephalitis, with renal adjustment, one-hour infusion and careful hydration.
- Neonatal disseminated or CNS HSV requires aciclovir 20 mg/kg intravenously every eight hours for 21 days; skin-eye-mouth disease requires 14 days under neonatal care.
- HSV keratitis needs same-day ophthalmology; topical antiviral and any corticosteroid phase must be directed by the corneal findings.
- Genital recurrence, suppression and pregnancy prevention are covered in the dedicated genital-herpes pathway; invasive and non-genital disease are emphasised here.
Key red flags
Fever with new confusion, personality change, focal seizure, dysphasia or reduced consciousness requires immediate encephalitis assessment and empirical intravenous aciclovir.
Eye pain, photophobia, red eye, reduced vision or a dendritic corneal lesion requires same-day ophthalmology and no unsupervised topical steroid.
Rapidly spreading painful monomorphic erosions with fever in eczema suggests eczema herpeticum and needs same-day systemic antiviral treatment.
A neonate with vesicles, lethargy, poor feeding, seizures, hepatitis or sepsis-like illness needs immediate intravenous aciclovir after urgent cultures and PCR samples.
Widespread mucocutaneous lesions, hepatitis, pneumonitis, coagulopathy or shock during pregnancy or immunosuppression suggests disseminated HSV.
Urinary retention, saddle sensory change or leg weakness can indicate HSV sacral radiculitis rather than uncomplicated genital or cutaneous disease.
Monomorphic punched-out erosions spread rapidly across eczematous skin with pain, fever and possible ocular or systemic involvement.
Unilateral red painful photophobic eye with reduced vision and a fluorescein-staining dendritic epithelial ulcer is sight threatening.
Investigation priorities
Confirm HSV and type an active mucocutaneous lesion.
Management branches
Fever and encephalopathy, focal seizure, dysphasia or compatible temporal features raise suspicion of viral encephalitis.
- Stabilise airway, breathing and circulation, treat seizures and hypoglycaemia, obtain blood cultures and cover bacterial meningitis when clinically indicated.
- Perform lumbar puncture promptly unless a specific contraindication requires imaging first; send cell count, protein, glucose and HSV or VZV PCR.
- Start intravenous aciclovir 10 mg/kg every eight hours within six hours if CSF or imaging will be delayed, the patient deteriorates or suspicion remains high.
- Use MRI and EEG, repeat CSF PCR when early results conflict with the syndrome and define a 14- to 21-day course with infection or neurology specialists.