16th July 2026

Viral Infections

Herpes Simplex Virus

Herpes simplex virus (HSV) is a double-stranded DNA virus responsible for a range of mucocutaneous infections. HSV-1 primarily causes orolabial lesions, whereas HSV-2 more commonly affects the genital region. However, either strain can infect any anatomic site depending on exposure. Following primary infection, the virus establishes latency in sensory ganglia, with the potential for reactivation under conditions such as stress, immunosuppression, or febrile illness.

Primary infection may present with fever, malaise, lymphadenopathy, and grouped vesicles on an erythematous base. It can be severe, especially in immunocompromised hosts. Recurrent infections tend to be milder. Other presentations include:

• Herpetic whitlow: painful vesicular lesions on the fingers, typically seen in healthcare workers or thumb-sucking children.
• Eczema herpeticum: widespread HSV infection in patients with atopic dermatitis — a medical emergency due to potential systemic spread.

Diagnosis

Diagnosis is usually clinical. Confirmatory tests are used in atypical or severe cases:

• PCR from vesicle fluid (most sensitive and specific)
• Viral culture (less common)
• Tzanck smear (obsolete)
• Direct fluorescent antibody testing in some labs

Management

• Mild to moderate: Oral aciclovir 400 mg TDS for 5 days (or valaciclovir/famciclovir)
• Severe/disseminated (eczema herpeticum): IV aciclovir
• Recurrent or frequent flares: Suppressive therapy (e.g. aciclovir 400 mg BD for 6–12 months)
• Counselling on avoiding direct contact during active lesions to prevent transmission

Herpes Zoster Virus (HZV)

Herpes zoster (HZV; shingles) results from reactivation of latent varicella-zoster virus (VZV) — the agent responsible for chickenpox. Following resolution of primary infection, VZV remains dormant in dorsal root or cranial nerve ganglia, reactivating years later, particularly in the elderly or immunocompromised.

It presents as a painful, unilateral vesicular rash distributed along a single dermatome. Prodromal burning, tingling, or hyperesthesia often precedes the rash by 1–3 days. Common sites include thoracic dermatomes and the trigeminal distribution.

Complications include:

• Postherpetic neuralgia (PHN) — persistent neuropathic pain lasting >3 months
• Herpes zoster ophthalmicus — involving the V1 branch; requires urgent ophthalmology referral
• Disseminated zoster in immunocompromised individuals

Diagnosis

Diagnosis is typically clinical. Consider PCR of vesicular fluid or skin biopsy in atypical presentations.

Management

• Antiviral therapy (start within 72 hours of rash onset):
  • Aciclovir 800 mg 5 times daily for 7 days
  • Alternatives: valaciclovir or famciclovir (better oral bioavailability)
• Analgesia:
  • Paracetamol/NSAIDs
  • Neuropathic agents for PHN (e.g. gabapentin, amitriptyline)
• Zoster vaccine is recommended for adults >50 years and those at increased risk