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Genital herpes simplex - Dr Deac Pimp

Definition

  • Sexually transmitted viral infection of the genitals caused by herpes simplex viruses HSV1 (mainly oral but can infect genitals) and HSV2 (mainly genital)

 

Risk factors

  • Sexual contact with infected person
  • Previous STIs
  • Current infection with other STIs
  • Risky sexual behaviour:
    • Chemsex
    • Group sex
    • Anal sex
    • Unknown sexual partners
    • Many sexual partners
  • MSM
  • HIV postitive
  • Immunocompromised
  • Female
  • Early age at first sexual encounter

 

Differential diagnoses

  • Candidiasis (very commonly misdiagnosed as herpes)
  • Genital warts
  • Syphilis
  • Chancroid
  • LGV (type of chlamydia)
  • Gonorrhoea
  • Chlamydia
  • Skin conditions:
    • Lichen sclerosus
    • Dermatitis
    • Scabies
    • Folliculitis
    • Psoriasis
  • Genital malignancy

 

Epidemiology

  • In the UK by age 25:
    • 60% carry HSV1 virus
    • 10% carry HSV2 virus
    • More within sexually active population
  • Over 31,000 first-time cases diagnosed in UK in 2014
  • Makes up 7% of total STI diagnoses
  • 42% are age 15-24
  • Rise in rates over past 10 years
    • 10% rise in MSM population from 2013 to 2014
  • HSV1 is now the most common cause of genital herpes
  • At least 80% of those infected with either HSV are unaware they carry it

 

Aetiology

  • Viral infection with HSV1 and HSV1
  • These are DNA virus that live in nerve cells (neurotrophic)
  • Transmission can be through sexual contact:
    • Oral, including kissing
    • Anal
    • Vaginal
    • Close genital contact
    • Condom use does not prevent transmission
  • Non-sexual contact with infected areas of skin
  • Transmission normally occurs during ‘shedding’ of the virus, which occurs in cycles

 

Clinical features

  • Can be asymptomatic
  • Typical infection has a well defined progression of symptoms:
    • Erythema and possible swelling of skin. May be painful or itchy
    • Painful thin walled blisters of clear or purulent fluid on an erythematous base
    • Blisters burst to leave ulcers
    • Ulcers scab over
    • Skin heals
  • Other local symptoms include:
    • Dysuria
    • Vaginal or urethral discharge
  • Systemic symptoms are most common in primary infection:
    • Fever
    • Myalgia
    • Tingling neuropathic pain in buttocks, genitals or legs
  • Many cases, especially HSV2, recur, normally several times a year, but are self-limiting and milder than the primary infection

 

Pathophysiology

  • Once the virus is acquired it takes up latency in local dorsal root sensory ganglia after 2 to 3 weeks
  • Around 1/3 of infections have a symptomatic first episode as a result of local infection
  • Not all infections will reactivate
  • Reactivation may be symptomatic or asymptomatic shedding of the virus
    • Both states are potentially transmissible
    • Primary infection is potentially transmissible

 

Investigations

  • Swabs taken from base of lesion
  • NAAT PCR testing for HSV specific DNA
  • Serology for HSV type-specific antibody
    • IgG detection indicates previous infection (may still be latent)
    • IgM is unreliable for recent/current infection
    • Antibodies take several weeks post-infection to develop
    • Serology is generally unreliable
  • Investigate the patient for other STIs
  • Contact tracing

 

Management

  • First episode:
    • Immediate antivirals based on clinical suspicion
      • Within 5 days of start of episode
      • Aciclovir 400mg TDS PO 5 days
      • OR Valaciclovir 500mg BD PO 5 days
      • Don’t use topical antivirals or core-sore medication
    • Supportive care:
      • Saline bathing (1 cup per bathtub)
      • Analgesia
      • Topical anaesthetic eg 5% lidocaine ointment
      • Counselling about transmission and natural history of the virus
  • Recurrences:
    • Early treatment before appearance of papules is most effective
    • Aciclovir 800mg TDS 2 days
    • Reduces severity and duration by 1-2 days
    • Suppressive antiviral therapy for >6 recurrences per year
      • Aciclovir 400mg DB PO
      • Reduces transmission by 50%

 

Prognosis

  • Complications:
    • Autonomic neuropathy
      • Urinary retention
    • Aseptic meningitis
    • Self-innoculation to other areas
    • Psychological and psychosexual problems
    • In comorbid HIV infection is increased risk of morbidity
    • Pregnancy:
      • Transmission perinatally
      • If HSV acquired before pregnancy or during 1st or 2nd trimester:
        • Treat the episode and plan vaginal delivery
        • Consider acyclovir 400mg TDS from 36 weeks prophylaxis
      • If HSV acquired in 3rd trimester:
        • Oral acyclovir 400mg TDS until delivery
        • Elective c-section (41% transmission risk with vaginal delivery)
    • Infection of baby:
      • 30% localised disease to skin/eye/mouth
        • 98% successfully treated
      • Local CNS disease ie encephalitis
        • Mortality 6%
        • Neurological morbidity 70%
      • Disseminated infection, even with treatment:
        • Mortality 30%
        • Neurological morbidity 17%
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