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15.3.1.1.1.2: Varicella Zoster Virus (HHV3)

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    Varicella-zoster Virus
    "Varicella-zoster Virus" by National Institutes of Health (NIH) is licensed under CC BY-NC 2.0

    Virus

    • Genetic material: double-stranded linear DNA
    • Virion structure: enveloped, icosahedral capsid

    Replication

    • DNA enters host nucleus and circularizes
      • Remains separate from host genome as episome
    • After initial infection, viral DNA remains in spinal root ganglia
      • Replication of virus (and therefore disease) can recur, usually due to stress, immune suppression, other disease, or exposure to factors which can cause DNA damage, such as sunlight (UV)

    Transmission

    • Virus enters through inhalation of respiratory droplets from an infected individual or touching eyes with virus-contaminated hands
    • Infected individuals are contagious before symptoms appear
    • Respiratory droplets and fluid from lesions are infective

    Epidemiology

    • Usually in children, but more dangerous in adults

    Clinical Disease

    • Chicken Pox (varicella):
      • rash appears 2 - 3 week after infection, starting on trunk and back and spreading over entire body (Figure \(\PageIndex{1}\))
        • macules (flat lesions) --> papules (raised lesions)--> fluid-filled vesicles on red base ("dew drops on rose petals")
      • other symptoms: fever, tiredness, loss of appetite, headache
    Varicella
    Figure \(\PageIndex{1}\): Chicken pox rash. ("Varicella" by nojhan is licensed under CC BY-SA 2.0)
    • Shingles (zoster):
      • occurs in about 15% of people who have had chicken pox
      • latent virus reactivated by stress, illness, chemotherapy, age, etc.
      • can be very painful
        • pain from inflamed nerves (from viral activity) can remain for months or years
      • rash only occurs in one band, usually on one side of torso or occasionally scalp
      • virus shed from shingles lesions can cause chicken pox in previously uninfected individuals

    clipboard_e93c85b08d72ae6c4984e023a33736713.png

    Figure \(\PageIndex{2}\): Shingles rash on A. torso and B. head. ("Shingles" by NIAID is licensed under CC BY 2.0)

    Treatement/Prevention

    • No treatment other than symptom relief (aspirin should not be given to children or adolescents)
    • Acyclovir can diminish symptoms in shingles, but does not cure it
    • Effective vaccine is available
      • children are routinely vaccinated against chicken pox
      • older adults can be vaccinated to prevent emergence of shingles (vaccine contains much higher dosage of same antigens as chicken pox vaccine)

    15.3.1.1.1.2: Varicella Zoster Virus (HHV3) is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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