Varicella Zoster

Question 1

Define Varicella Zoster.

Answer 1

Primary infection is called varicella (chickenpox). Reactivation of the dormant virus in the dorsal root ganglia, causes zoster (shingles)

Question 2

What is the epidemiology of VZ?

Answer 2

• Chickenpox peak incidence - 4-10yrs old
• Shingles peak incidence >50yrs
• About 90% of adults are VZV IgG positive

Question 3

Which human herpesvirus is VZV? What is the mode of transmission?

Answer 3

HHV- - respiratory transmission

Question 4

What is the incubation period of varicella zoster?

Answer 4

9-21 days

It is exclusively a human virus

Question 5

What is the pathophysiology of VZV?

Answer 5

• Primary infection with human alpha herpes virus by direct contact with lesions or airborne spread through respiratory droplets.
• Virus spreads to lymph nodes, then days 4-6 to the liver, splees and other reticuloendothelial cells.
• By day 9, mononuclear cells spread the virus to the skin and mucous membranes –> vesicular rash. VZV –> vasculitis of small vessels and degeneration of epithelial cells leading to vesicles with fluid with high viral load.
• Patients are therefore infectious before rash develops and for 5 days/until all the lesions have crusted over.
• Incubation is typically 14 days

Question 6

Which patients are at risk of severe VZV disease?

Answer 6

• Patients who are immunocompromised (e.g., organ transplant, chemotherapy, HIV infection)
• Neonates
• Those taking chronic oral corticosteroids or high-dose systemic immunosuppressants
• Pregnant women

Question 7

What are the risk factors for VZV?

Answer 7

• Age 1-9yrs
• Exposure to varicella - family contacts or day care- or school-related exposure.
• Unimmunised
• Occupational exposure

Question 8

Describe the presentation of chickenpox.

Answer 8

• Prodromal malaise
• Mild pyrexia
• Generalised pruritic, vesicular rash - face and trunk predominantly
• Contagious from 48hr before rash and until all vesicles have crusted over (within 7-10days)

Question 9

Describe the presentation of shingles.

Answer 9

• May occur due to stress
• Tingling in a dermatomal distribution
• Followed by painful skin lesions
• Recovery in 10-14days

Question 10

What investigations would you do for varicella zoster?

Answer 10

Clinical diagnosis

• PCR - positive for virus DNA
• Viral culture
• ELISA, LA (latex agglutination +ve for IgG), Tzanck smear, DFA (direct fluorescent antibody testing),

Question 11

How do you manage acute varicella zoster?

Answer 11

Children:

• Treat symptoms
  
  • Calamine lotion
  • Analgesia
  • Antihistamines

Adults:

• Consider aciclovir, valaciclovir or famciclovir if within 24h of rash onset

Question 12

How do you manage varicella zoster reactivation?

Answer 12

• 1st line - valaciclovir, famciclovir
• 2nd line - acyclovir

If within 72hr of appearance of the rash for 7 days

Prevention: VZIG may be indicated if immunocompromised, pregnant and exposed to varicella zoster.

Question 13

What are the complications of VZV? What is the prognosis?

Answer 13

Prognosis - typically self-limiting, up to a third reactivates later in life as shingles or herpes zoster.

• Reye’s synrome - if children given NSAIDs (30% fatality) - presents with vomiting, encephalopathy, and metabolic disturbances such as hyperammonaemia and elevated liver enzymes
• Bacterial sepsis
• Encephalitis
• Haemorrhagic complications
• Postherpetic neuralgia
• Meningoencephalitis
• Myelitis
• Cranial nerve palsies
• Vasculopathy
• GI ulcers
• Pancreatitis
• Hepatitis

Question 14

What is a unilateral vesicular rash around the eye likely to be a presentation of? Which branch of the nerve is affected?

Answer 14

Herpes zoster reactivation in trigeminal nerve = herpes zoster ophthalmicus

Question 15

What are the complications of herpes zoster ophthalmicus?

Answer 15

• corneal ulcers (‘pseudodendritic’ ulcers),
• uveitis
• involvement of the retina or optic nerve
• extraocular muscle palsies (rarely)

Question 16

What is the sign when the tip of the nose is affected in herpes zoster ophthalmicus?

Answer 16

If the tip of the nose is affected by the rash, then the nasociliary nerve is involved, and thus the eyeball is more likely also to be involved (Hutchinson’s sign).

Treatment: Systemic antiviral therapy (acyclovir) given promptly reduces the risk of post herpetic neuralgia. In addition, ophthalmic assessment may lead to topical antivirals and possibly topical steroids being advised, but this can only follow ophthalmic assessment.