🦠 Herpes Simplex Virus (HSV) causes recurrent vesicles → ulcers affecting oral 👄, genital ⚤, ocular 👁️ and (rarely) CNS 🧠. HSV-1 is classically oral (but increasingly genital), while HSV-2 is classically genital. After primary infection, HSV becomes latent in sensory ganglia (trigeminal or sacral) and can reactivate with triggers like fever, UV light, stress, friction, and immunosuppression 🔁.

🧬 Virology & Pathophysiology

Family: Herpesviridae (alpha-herpesviruses) - enveloped, double-stranded DNA virus.
4-layer structure: 📦 DNA core → ⬡ icosahedral capsid → 🧩 tegument proteins → 🧪 lipid envelope with glycoproteins (entry + immune evasion).
Latency: virus persists in neurons; reactivation travels down the nerve → local epithelial infection → clustered vesicles.
Why recurrence happens: local immune control suppresses but rarely eradicates HSV; reactivation is often milder than the first episode.

📌 Transmission & Infection Control

HSV-1: mainly oral contact 💋 (saliva, kissing), but also genital via oral–genital contact.
HSV-2: mainly sexual contact ⚤.
Asymptomatic shedding: common (especially genital HSV) → transmission can occur without visible lesions.
Advice: avoid kissing/sex during outbreaks; condoms reduce (not eliminate) transmission; don’t share lip balms/razors during active lesions.

👄 HSV-1 Typical Clinical Syndromes

Herpes labialis (cold sores): prodrome (tingle/burn) → vesicles on lip border → crusting.
Primary herpetic gingivostomatitis: fever 🤒, painful oral ulcers, poor intake/dehydration risk (esp. children).
Herpetic whitlow: painful finger vesicles (healthcare exposure risk) 👩‍⚕️.
Herpes keratitis: red/painful eye, photophobia; dendritic ulcer on fluorescein ✨ (urgent ophthalmology) 👁️.
HSV encephalitis: fever, confusion, seizures, focal signs; classically temporal lobe involvement 🧠⚡ (treat immediately).

⚤ HSV-2 Typical Clinical Syndromes

Genital herpes: painful vesicles/ulcers, dysuria, tender inguinal nodes; systemic symptoms may occur in primary episodes.
Anorectal HSV: proctitis, rectal pain, discharge, tenesmus.
Neonatal HSV: can be disseminated, CNS, or skin/eye/mouth disease 👶 (medical emergency).

🚨 Red flags (same-day / emergency) Suspected HSV encephalitis (fever + confusion/seizures/focal deficits) → start IV aciclovir immediately. Ocular HSV symptoms (eye pain, photophobia, reduced vision) → urgent ophthalmology. Eczema herpeticum (widespread painful monomorphic “punched-out” erosions in eczema) → urgent antivirals ± admission. Neonatal disease or immunocompromised host with widespread lesions/systemic illness.

🔍 Differential Diagnosis

Herpes zoster (dermatomal, unilateral, neuropathic pain) ⚡
Impetigo (honey-coloured crusts) 🧫
Hand-foot-and-mouth disease (enterovirus) 👶
Syphilis / chancroid and other STI ulcer causes ⚤
Aphthous ulcers, traumatic ulcers, contact dermatitis

🧪 Diagnosis

Clinical diagnosis is often sufficient for typical cold sores.
Genital/or atypical lesions: swab for PCR/NAAT (preferred test) ✅
Encephalitis: CSF HSV PCR (but do not wait for results before treatment) 🧠
Serology: may help define past exposure, but is not useful for diagnosing a current lesion.

💊 Treatment Overview

Best timing: antivirals work best if started early (prodrome/within ~48 hours) ⏱️
Options: aciclovir, valaciclovir, famciclovir (choice depends on severity, site, and adherence).
Supportive care: analgesia, hydration, saline bathing, avoid picking lesions; topical lidocaine gel may help painful ulcers.

📋 Genital Herpes (UK-style) - Common Regimens

Scenario	Example regimen	Notes
First episode ⚤	Aciclovir 400 mg TDS (or 200 mg 5×/day) for 5–10 days OR Valaciclovir 500 mg BD for 5–10 days	Treat longer if new lesions still forming or slow healing.
Recurrent episode 🔁	Aciclovir 400 mg TDS for 5 days OR Valaciclovir 500 mg BD for 3–5 days	Patient-initiated “episodic” therapy works best started at prodrome.
Suppressive therapy 🛡️	Aciclovir 400 mg BD OR Valaciclovir 500 mg OD (or 1 g OD if frequent recurrences)	Consider if frequent recurrences, severe symptoms, psychological distress, or to reduce transmission risk (not zero).

🧠 HSV Encephalitis - Key Management Points

Think of it early: fever + altered behaviour/confusion, seizures, focal deficits, or new neuropsychiatric symptoms.
Treatment is time-critical: start IV aciclovir immediately if suspected 🚨
Typical adult dose: IV aciclovir 10 mg/kg every 8 hours (dose-adjust in renal impairment).
Duration: commonly 14–21 days, guided by clinical course and specialist advice.

🧴 Cold Sores (Herpes Labialis) - Practical Advice

Self-care: petroleum jelly to prevent cracking, avoid triggers (UV/trauma), don’t share lip products during outbreaks 💋
Topical antivirals: can modestly shorten symptoms if started early; adherence is key.
Oral antivirals: consider for severe/frequent episodes or immunocompromised patients (local guidance varies).

🧑‍⚕️ Special Situations

Eczema herpeticum 🧴🔥: urgent systemic antivirals; admit if unwell, extensive disease, eye involvement, or immunosuppressed.
Pregnancy 🤰: primary genital HSV near delivery needs urgent obstetric review due to neonatal risk.
Immunocompromised 🛡️: lower threshold for systemic therapy; consider dissemination/organ involvement.

🖼️ Figures (add to your page as needed)

Fig 5.8: Herpes simplex in darker skin - Skin Deep (2022).
Fig 5.9: Herpes simplex in lighter skin - Skin Deep (2022).

📚 References

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Herpes Simplex Virus