Varicella Zoster Virus

Question 1

VZV

Answer 1

DNA - Herpesvidriae Alpha

• Short reproductive cycle
• Efficient cell dstruction
• Rapid spread in culture
• Latency in sensory ganglia

Peds - Chicken Pox
Adult - Zoster (lifelong latency)

Question 2

VZV - Varicella’s Pathogenesis & Immune Response

Answer 2

1) Infection respiratory tract and conjunctiva - Day 1: Asymptomatic (NK cells and INF-y)
2) Local replication in upper airway and lymph node
3) Primary viremia and infection of lymphocytes and nerve cells (Initial T cell response)
4) Replication and secondary viremia - Fever, malaise (Expanding T cell response)
5) Infection of skin - Day 10-21: Rash (INF-a in skin)

Question 3

VZV - Immune privileged sites

Answer 3

Def: tissues that are protected from immune system

Examples: brain, nerves, eye, testes, placenta/fetus

Question 4

VZV - decline of T cell immunity

Answer 4

anti-VZV memory T cells prevent reactivation
Decline as we age, when fall below a critical threshold -> boost in anti-ZVZ immunity
Hence, why recurrent shingles is rare

Question 5

VZV - Zoster’s pathogensis

Answer 5

Replication in DRG -> migration along sensory nerve (dermatomal manifestation) -> rash -> damage to nerve cell

Question 6

VZV - High Risk Group

Answer 6

Disseminated Disease
- T cell absence (HIV/Chemoteraphy)

Shingles
- T cell dysfunction or absence, older patients

Question 7

VZV - Varicella’s Clinical Manifestations

Answer 7

Very ITCHY!
Central distribution + mucous membranes (mouth, conjunctiva, vagina)
Temperate > Tropical Climates (Late winter and spring)
Secondary attack rate: 90% of household embers
- Transmission: respiratory secretion & direct fluid contact from vesicles

Vesicular Rash Progression (200-500)
Papules -> Vesicles (Clear) -> Vesicles (Cloudy) -> Crusting(within 5-7 days)
*all stages appears simultaneously

Complications:

• Pneumonitis
• Hepatitis
• Encephalitis

Question 8

VZV - Zoster’s Clinical Manifestations

Answer 8

PAINFUL
>45 risk group & >60 highest risk
dermatomes distribution (unilateral and central)
Apperance similar to varicella except crusting by day 14

Complications:

• Secondary bacterial infection of the lesion: Staph A, Strep pyo, cellulitis, abscess
• Disseminated disease: immunocompromised patients
• Post Herpetic Neuralgia (PHN) 20% of patient mostly eldery -> pains for months to years

Question 9

VZV - Diagnosis

Answer 9

Clinical diagnosis: Prodrome & Rash appearance + progression
PCR on vesicular fluid

Question 10

VZV - Varicella Treatment

Answer 10

Symptom control

Prevention of secondary infection

Anti-viral therapy in selected patients: adolescents/adults/immunocompromised patients

Acyclovir

Question 11

Acyclovir, Valacyclovir

Answer 11

MOA: Inhibition of viral DNA polymerase

Usage: Varicella-Zoster Virus (HHV-3) - Resistance: mutation in thymidine kinase gene

Question 12

Famciclovir

Answer 12

MOA: Retardation, nucleoside incorporation

Usage: Varicella-Zoster Virus (HHV-3) - Resistance: mutation in thymidine kinase gene

Question 13

VZV - Zoster Treatment

Answer 13

Antiviral medications -> speed up resolution of rash & reduce PHN, pain management

Question 14

VZV - Varicella Prevention

Answer 14

LAVV (OKA strain)
Varicella vaccine + MMRV
1 yo and 4-6 yo
DO NOT give to ImmCp or pregnant patient

Question 15

VZV - Zoster Prevention

Answer 15

LAVV (OKA strain higher dose)
Routine immunization >60 yo
Decrease shingles by 50%; PHN by 67% (effective in 60-69)

Immunoglobulins if can’t immunize

Acyclovir early during incubation