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.

Prevention

  • Avoidance of varicella is the only guaranteed method of preventing complications
    • Patients infected with varicella zoster virus (VZV) are contagious for 24-48 hours prior to the emergence of clinical signs until 5-6 days after onset of rash, during which vesicles have evolved into dried crusts

Active Prophylaxis

Herpes Zoster Vaccine

  • A high dose live-attenuated vaccine of the Oka strain; 14 times more potent that VZV vaccine
  • Several studies have shown that this vaccine can reduce the incidence of herpes zoster, the burden of illness, and the incidence of post-herpetic neuralgia (PHN)
  • Recommended for patients aged >60 years old
  • Should not be used in the presence of acute febrile illness, active untreated tuberculosis, or pregnancy

Varicella Zoster Virus Vaccine

  • Live attenuated vaccine of the Oka strain that provides long-lasting resistance against varicella
    • The vaccine strain causes subclinical VZV infection in vaccinees and leads to immunity
    • As a live herpes virus, it may establish latency and reactivate later on
  • May be given to immunocompetent individuals >12 months of age who do not have a history of VZV infection
    • 1st dose is given at age 12-15 months and 2nd dose at age 4-6 years
    • Non-immunized adults and adolescents >12 years are recommended to have 2 doses given 4-8 weeks apart
    • Children >12 months infected with human immunodeficiency virus (HIV) with age-specific CD4+ T-lymphocyte percentages of ≥ 15% should receive 2 doses, given 3 months apart
    • HIV-infected individuals >8 years with CD4 counts ≥200 microL should also receive 2 doses, given 3 months apart
  • A high-titer VZV vaccine can be given to adults >50 years old which will decrease incidence of herpes zoster infection, disease burden, and postherpetic neuralgia (PHN)
  • Contraindicated in immunocompromised or pregnant patients & infants <12 months

Passive Prophylaxis

Varicella Zoster Virus Immunoglobulin G (VZV IgG/ VZIG)

  • A high-titer preparation of VZV IgG antibodies
    • Improves symptoms of chickenpox in high-risk individuals
  • May be given to susceptible high-risk individuals including immunocompromised children without a history of VZV infection and pregnant women without history of VZV and no antibody to VZV who have had a close exposure to an individual with varicella or herpes zoster
    • May also be considered in newborn infants born to mothers with signs and symptoms of infection within 5 days before to 2 days after delivery
    • May also be considered in premature infants born at ≥ 28 weeks of gestation with postnatal exposure and whose mothers have no evidence of immunity
    • <28 weeks age of gestation (AOG)-born hospitalized premature infants regardless if the mother is with or without VZV infection
    • Not generally recommended in healthy susceptible adults since these patients can be given oral antivirals if varicella infection develops
  • Administer within 10 days post-exposure; ideally within 96 hours (4 days) post-exposure
  • Effects: Patients may still develop varicella despite VZIG but the risk of varicella pneumonia is significantly reduced if passive prophylaxis is used

Post-exposure Prophylaxis

Varicella Zoster Virus Vaccine

  • Varicella vaccine is recommended in susceptible individuals after exposure to varicella
  • Varicella vaccine is effective in preventing illness or modifying varicella severity if given within 3 days and potentially up to 5 days after exposure
  • If the exposure did result in infection, the administration of varicella vaccine during prodromal stage does not appear to increase the risk for vaccine-related adverse effects
  • Contraindicated in immunocompromised or pregnant patients

Further Evaluation

  • Further evaluation is needed especially in immunocompromised patients
  • Observe for the following in varicella zoster virus (VZV) infection:
    • Other bacterial, neurologic, respiratory, hepatic, hematologic complications
    • Appearance of rash in dermatomal distribution that is predictive of herpes zoster which usually follows latent period of many years
  • Observe for the following in herpes zoster:
    • Other bacterial, neurologic, ophthalmic, respiratory, hepatic, hematologic complications
    • Persistent pain after 1-3 months of rash resolution is suggestive of postherpetic neuralgia
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