Varicella-zoster Virus

Question 1

Classification

Answer 1

Family: Herpesviridae

Genus: varicellovirus

Species:

Common name: Varicella Zoster Virus

Official name: HHV3

Question 2

Characteristics

Answer 2

• enveloped virus
• icosehedral nucleocapsid
• linear, dsDNA
• no virion polymerase
• one serotype
• replicates in the nucleus of the host cell —> produces intranuclear inclusion bodies

Question 3

Transmission

Answer 3

> Varicella

MAIN: respiratory droplets

OTHER: vertical transmission (Congenital varicella syndrome)

> Zoster

NOT TRANSMITTED (latent reactivation)

Question 4

Pathogenesis

Answer 4

• Initial infection is in the oropharynx
• it spreads via the blood to the internal organs, such as the liver and then to the skin
• after acute episode of varicella:
  »> the virus remains latent in the sensory thoracic ganglia

Can reactivate to cause Zoster years later, especially in the elderly and immunocompromised, also by stress

Question 5

Disease

Answer 5

Varicella (chicken pox):

• Common in children
• exanthem (sudden rash)
• associated with headache and fever
• Vesicular lesion (dew drops on a rose rash)

> > > these lesions are all in different stages of healing (ie. blisters, healing scabs)

> > > in adults it leads to complication if they are immunocompromised:
pneumonia
encephalitis

• congenital varicella syndrome:
  > limb hypoplasia
  > cutaneous dermatomal scarring
  > blindness
• Zoster (shingles) in adults (very painful)
  »> with dermatological distribution
  »> dew drops on a rose petal rash
  »> post-herpetic neuralgia: pain after rash subsides

vision loss if dermatomal distribution reaches the V1 ganglion of trigeminal nerve&raquo_space;> Herpes-zoster ophthalmicus

Question 6

Microbiological diagnosis

Answer 6

• detection: CPE in cell culture
• multinucleated giant cells —> Tzanck smear
  »> intranuclear inclusion seen in infected cells
• a four-fold or greater rise in antibody titer in covalescent-phase serum is diagnostic

Question 7

Treatment and prevention

Answer 7

Treatment:
For variocella: acyclovir
For zoster: Famcyclovir, Acyclovir and valacyclovir

Prevention:

• Varicella live-attenuated vaccine —> children
• Zoster live-attenuated vaccine:
  »> elderly > 60 yrs
  »> HIV + patients with CD4 count >200

Immunocompromised patients exposed to the virus should receive passive immunization with varicella-zoster immune globulin and acyclovir to prevent disseminated disease