varicella-zoster%20virus%20infection
VARICELLA-ZOSTER VIRUS INFECTION
Varicella, also known as chickenpox, is a self-limited benign disease caused by primary varicella-zoster virus (VZV) infection characterized by fever, malaise, and generalized pruritic vesicular rash.
The average incubation period is 14-16 days. It is transmitted via direct contact with vesicular fluid or inhalation of aerosolized respiratory secretions or via droplet route during face-to-face contact.
Hallmark sign is pruritic rash that begins in the scalp and face which eventually spreads to the trunks and extremities.

Definition

Varicella

  • Also known as chickenpox although transmitted only by humans
  • A self-limited systemic infectious disease caused by primary varicella-zoster virus (VZV) infection
  • Characterized by fever, malaise, and generalized, pruritic, vesicular rash

Herpes Zoster

  • Also known as shingles
  • Results from recrudescence of latent VZV from dorsal root or cranial nerve ganglia that has been present since primary infection with varicella

Etiology

Varicella

  • Double-stranded DNA virus that contains the smallest genome of the herpes viruses
  • Incubation period: 10-21 days (average: 14-16 days)
  • Transmitted via direct contact with vesicular fluid, inhalation of aerosolized respiratory secretions or via droplet by airborne route, or during face-to-face contact
  • Highly infectious to non-immunized contacts 48 hours before the appearance of rash until 5-6 days after onset of rash, during which vesicles have evolved into dried crusts
  • After recovery from infection, virus remains dormant in dorsal root ganglia and reactivate later as shingles once the host becomes immunocompromised

Herpes Zoster

  • VZV initially enters epidermal cells and manifests as the typical varicella rash, moves into sensory nerves at mucocutaneous sites then travels by retrograde axonal transport to the sensory dorsal root ganglia where the virus remains non-infectious in its latent form inside neuronal cell bodies until reactivated
  • Less contagious than varicella but may cause varicella in susceptible persons
  • Risk of developing shingles increases with age

Signs and Symptoms

Varicella

  • Prodrome of fever (<38.9°C), headache, malaise, pharyngitis and abdominal pain may occur 1-2 days before development of rash in older children and adults
    • In younger children, the rash and fever typically occur simultaneously without prodromal symptoms
  • Hallmark sign is pruritic rash that begins on the scalp and face which eventually spreads to the trunks and extremities
    • Initially, erythematous macules then to maculopapular phase to vesicular
    • Small fluid-filled vesicles with an erythematous base that has “dewdrop-on-a-rose-petal” appearance
    • Within 24-48 hours, the vesicles transform into pustules that crust and scab within 6 days
    • New lesions may arise in successive crops over 3-4 days
    • Lesions are in varying stages of development
  • Ulcerative & often painful lesions appear on mucous membranes including the oropharynx, conjunctivae & vagina
  • Breakthrough cases, occurring >42 days after vaccination, generally present with milder symptoms, <50 skin lesions appearing as atypical maculopapular rashes with few or no vesicles

Herpes Zoster

  • Prodromal symptoms of fever, headache, malaise, pruritus, hyperesthesia or paresthesia described as burning, deep aching, tingling, itching or stabbing pain that ranges from mild to severe, in the affected dermatome may occur days to weeks before development of rash
  • Prodromal phase is followed by pruritic, vesicular rash that usually appears unilaterally along the thoracic, cervical & ophthalmic dermatomes without crossing the midline
    • Initially, it appears as maculopapular rash that follows a dermatomal distribution, commonly referred to as “belt-like pattern”
    • Evolves into vesicles with an erythematous base
    • Vesicles are often painful and their development can be accompanied by anxiety and flu-like symptoms
    • Vesicles often coalesce into larger, fluid-filled or pustular lesions, become hemorrhagic or ulcerated, then crust within 7-10 days and fall off within 2-4 weeks; may leave scars or pigmentary changes
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