Medicine & USMLE

Herpes Simplex Virus 1 (HSV1)

Viruses - DNA Viruses
  1. Herpesvirus Overview
  2. Herpes Simplex Virus 1 (HSV1)
  3. Herpes Simplex Virus 2 (HSV2)
  4. Varicella-Zoster Virus (HHV3)
  5. Epstein-Barr Virus (HHV4)
  6. Cytomegalovirus (HHV5)
  7. Human Herpesviruses 6 and 7 (HHV6 and HHV7)
  8. Human Herpesviruses 8 (HHV8)
  9. Poxvirus
  10. Hepadnavirus
  11. Adenovirus
  12. Papillomavirus (HPV)
  13. Polyomavirus
  14. Parvovirus

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