Herpes Simplex Virus 1 (HSV1)

Key Points

• Herpes simplex virus 1 (HSV-1)
  • Characteristics
    • Member of Herpesvirus family
      • Also known as human herpesvirus 1 (HHV-1)
      • Enveloped DNA virus with double-stranded, linear DNA 
        • Herpesviruses are unique in that they get their envelope by budding from nuclear membrane of host cell
  • Transmission
    • Contact with infected lesions
      • oral-oral, oral-genital, or genital-genital contact
  • Pathophysiology and Presentation
    • Viral infection manifests as grouped vesicles on erythematous base
      • Can ulcerate, leading to lesions in various states of healing (vesicles, pustulations, ulcers, scabbing, etc.)
    • Primary infection
      • Virus replicates at site of exposure
      • Gingivostomatitis
        • Commonly occurs in children 1-3 years old
        • Fever, vesicles and ulcers along oral mucous membranes, and cervical lymphadenopathy
      • Pharyngitis may be primary symptom in adults
      • Herpetic whitlow (finger ulcer)
        • Primary infection of skin in fingers
        • Caused by touching infected lesions with hands
          • Seen in children who touch infected lesions or occupational exposures (e.g. dentists)
    • Dormancy in sensory ganglia
      • Enters sensory nerve and moves via retrograde transport from mouth or genitals
        • Rarely seen from finger (whitlow); sensory neuron is too long
      • Lifelong dormancy in trigeminal ganglia or sacral ganglia depending on site of initial infection
    • Reactivation
      • Replicates in ganglia with anterograde transport to epithelial cells, where virus continues to replicate
      • Herpes labialis (oral-labial ulcers)
        • Also known as “cold sores” or “fever blisters”
        • Tends to favor skin around lips and nose
        • Caused by reactivation of HSV-1 in trigeminal ganglia
        • Genital lesions may be seen by reactivation from sacral ganglia, but is rarer
      • Erythema multiforme (EM)
        • Most common trigger for EM
        • Immune-mediated response to HSV-1 infection
      • Keratoconjunctivitis
        • Rare cause of blindness in developing countries without treatment
      • Severe symptoms in immunocompromised patients (e.g. HIV)
        • Encephalitis
          • Primarily affects temporal lobe
          • Presents as fever, altered mental status, seizures, focal neurologic deficits
          • CSF shows viral pattern
            • hemorrhagic (RBC) pleocytosis
            • predominant lymphocytes
            • increased protein
            • normal glucose
        • Esophagitis
          • Punched out ulcers on endoscopy
          • Presents as dysphagia or odynophagia
          • Especially common in AIDS
        • Hepatitis, Bell’s palsy, and epiglottitis/laryngitis are also seen
  • Diagnosis
    • PCR and viral culture is gold standard
    • Tzank smear of lesions
      • Epithelial cells scraped from lesion, prepared on Wright-Giemsa stain
      • Multinuclear giant cells
        • intranuclear inclusions (Cowdry type A bodies)
      • High yield; but not used clinically due to poor sensitivity/specificity
  • Treatment
    • Acyclovir and related drugs (famciclovir/valacyclovir)
      • Guanosine analog that inhibit viral DNA polymerase (viral DNA synthesis)
      • Requires herpes viral thymidine kinases (phosphorylation) for conversion into their active form