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Herpes simplex virus

Medicine > Infection

Background knowledge 🧠

Definition

  • Herpes simplex virus (HSV) is a DNA virus that causes infections in humans.
  • There are two types: HSV-1 (primarily oral) and HSV-2 (primarily genital).
  • Both types can cause infections at either site.
  • Characterised by latent infection and periodic reactivation.
  • Transmission occurs through direct contact with infected body fluids.

Epidemiology

  • HSV-1 is more common globally, typically acquired in childhood.
    • Approximately 67% of the global population under 50 has HSV-1.
  • HSV-2 prevalence higher in sexually active adults.
    • Around 11% of the global population aged 15-49 has HSV-2.
  • Higher prevalence in women and in regions with higher HIV prevalence.
  • Reactivation risk increases with immunosuppression and stress.

Aetiology and pathophysiology

  • Caused by Herpes simplex virus types 1 and 2.
  • Primary infection: virus enters through mucous membranes or skin breaks.
  • Virus travels to sensory neurons and establishes latency.
  • Reactivation: triggered by factors like stress, illness, or immunosuppression.
  • Recurrent infections typically less severe than primary infection.
  • Viral shedding can occur asymptomatically, contributing to transmission.

Types

  • HSV-1: primarily causes oral herpes (cold sores), but can cause genital herpes.
  • HSV-2: primarily causes genital herpes, but can cause oral herpes.
  • Both types can cause herpetic whitlow (finger infection) and herpes gladiatorum (skin infection).
  • Neonatal herpes: severe infection in newborns, typically from HSV-2.
  • Herpes encephalitis: a rare but serious infection of the brain, often from HSV-1.

Clinical Features 🌡️

Symptoms

  • Oral herpes: painful blisters or ulcers on lips or around the mouth.
  • Genital herpes: painful blisters or ulcers on the genitaloranal area.
  • Prodromal symptoms: tingling, itching, or pain before the appearance of blisters.
  • Systemic symptoms in primary infection: fever, malaise, lymphadenopathy.

Signs

  • Grouped vesicles on an erythematous base.
  • Crusting and healing of vesicles over 7-10 days.
  • Erythema and swelling in affected areas.
  • Lymphadenopathy in regional nodes.
  • In severe cases: keratoconjunctivitis, herpetic whitlow,oropharyngeal ulcers, pharyngitis or encephalitis.

Investigations 🧪

Tests

  • Viral PCR from lesion swabs: gold standard for diagnosis.
  • Serology: detects HSV antibodies, useful for past exposure.
  • Lumbar puncture and CSF analysis for suspected herpes encephalitis.
  • Ophthalmologic examination for suspected herpetic keratitis.
  • Biopsy and histopathology in atypical cases.
  • HIV testing recommended in patients with genital HSV due to co-infection risk.

Management 🥼

Management

  • Antiviral therapy: aciclovir, valaciclovir, famciclovir for primary and recurrent infections.
  • Topical antivirals for mild oral herpes.
  • Chronic suppressive therapy for frequent recurrences.
  • Pain management: analgesics and topical anesthetics.
  • Education on avoiding triggers and reducing transmission risk.
  • In severe cases: hospitalisation and intravenous antivirals.
  • Regular follow-up for patients with frequent recurrences or complications.
  • Counselling and support for patients with significant psychological impact.

Complications

  • Herpetic keratitis: can lead to corneal scarring and vision loss.
  • Herpes encephalitis: potentially life-threatening brain infection.
  • Neonatal herpes: severe infection in newborns, high mortality.
  • Secondary bacterial infection of skin lesions.
  • Psychological impact: anxiety, depression, social stigma.
  • Chronic pain: post-herpetic neuralgia.
  • Transmission to sexual partners or during childbirth.
  • Increased risk of HIV acquisition and transmission.
  • Systemic involvement in immunocompromised individuals.

Prognosis

  • Good prognosis with antiviral treatment for most cases.
  • Recurrent infections common, but tend to be less severe.
  • Chronic suppressive therapy reduces frequency and severity of recurrences.
  • Severe complications more likely in immunocompromised individuals.
  • Education on disease management improves quality of life.
  • Regular follow-up important for patients with frequent recurrences or complications.
  • Prognosis poorer in cases of disseminated infection or encephalitis.

Key points

  • Herpes simplex virus (HSV) causes lifelong infections with periodic reactivations.
  • Antiviral therapy effective in managing symptoms and reducing transmission.
  • Education on prevention and early treatment critical for reducing complications.
  • Frequent recurrences and severe complications more common in immunocompromised individuals.
  • Psychological support important for managing the emotional impact of the infection.
  • Regular follow-up and patient education improve outcomes and quality of life.
  • Awareness of asymptomatic shedding is crucial for preventing transmission.
  • Multidisciplinary approach may be needed for managing complex or severe cases.

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Infection