Varicella Zoster Virus (VZV)
What species is VZV?
*Human herpesvirus 3*
What are the characteristics of all herpesviruses?
-Latency -DNA genome -In general, do not show fomite transmission
Why are you encouraged not to scratch chicken pox lesions?
1) Secondary bacterial infections, especially S. pyogenes 2) Scarring
When does the rash appear in VZV?
14 days post infection. Approximately 3 days after secondary viremia.
What percentage of adults who have had chicken pox will develop shingles in their lifetime?
30%
What are the clinical manifestations of chicken pox?
A maculopapular rash that appears 14 days after infection and begins on the trunk. Primary lesions are 2-4 mm red papule with irregular outline (rose petal). Next a clear vesicle forms on the red papule (*dew drops of a rose petal*). Within 12 hours the vesicle becomes pustular and begins to crust, after which, scabs appear. By day 7, most lesions are formed scabs. *All stages of lesions can be observed at a given time. This is a hallmark of chicken pox*. Lesions are pruritic and more severe on the trunk. Fewer lesions on the extremities than the trunk. Few or no lesions on the palms and soles.
What is Varizig (Cangene)?
A varicella immune globulin used to reduce the severity of VZV infections in high risk individuals. Must be given within 4 days of exposure. The only FDA approved post-exposure prophylaxis for VZV.
What are the treatments of VZV in adults and immunocompromised patients with VZV or herpes zoster?
Acyclovir, famcyclovir and valacyclovir. Immunocompromised individuals and newborns of symptomatic mothers can be given VZIg.
Is primary infection of chicken pox more serious in adults or children?
Adults. Their robust immune systems lead to more complications.
Why is breakthrough varicella still a concern?
Because an infected child can still transmit varicella to others.
Why is laboratory diagnosis of varicella becoming more important?
Because there are fewer and fewer cases of chicken pox, and chickenpox in vaccinated people is often mild or atypical.
How is MLVS different from VZV?
Breakthrough varicella rashes may be more maculopapular than vesicular, there may be fewer than 50 lesions (compared to 300), and no fever.
What is zoster sin herpete?
Herpes zoster without the rash.
To what family does VZV belong?
Herpesviridae
What are the clinical manifestations of herpes zoster?
Herpetic rash and sever neuronal pain along specific dermatomes. Lesions usually resolve within 7 to 10 days but complete healing may take 4 weeks. Longer in immunocompromised.
What are the known reservoirs of VZV?
Humans are the only known reservoir.
Where does VZV establish latency?
In the trigeminal ganglion, dorsal root ganglions, and cranial ganglia.
What individuals are at highest risk for severe complications from chicken pox?
Infants, adolescents, adults, pregnant women and immunocompromised.
What are the complications of chicken pox in adults?
Interstitial pneumonia (20-30%), encephalitis, seizures, difficulty walking (cerebellar ataxia), secondary bacterial infections, sepsis, TSS, etc.
What is breakthrough varicella or MLVS?
Mild varicella-like syndrome refers to infection in previously vaccinated individuals (1-3% of children).
Is shingles contagious before the rash appears?
No
Can you get herpes zoster from someone with herpes zoster?
No, you will catch a primary varicella zoster infection (chicken pox).
Does VZV have seasonal incidence?
No. Anywhere in the world, any time of year.
Is the presence of syncytia enough to make a lab diagnosis of VZV?
No. Many viruses operate via syncytial formation.
What is the most sensitive method for confirming varicella?
PCR. Sample is acquired from the skin lesions.
What is the most common complication of herpes zoster?
Postherpetic neuralgia (PHN), a chronic syndrome of at least 90 days, that can last for months to years. Suicide is prevalent in this population. 5% of those < 60 years 20% > 80 years
What does VZV cause?
Primary - chicken pox Secondary -Shingles (Herpes Zoster)
What is chicken pox infection in neonates called?
Progressive-disseminated varicella. It can be fatal.
What is herpes zoster?
Shingles
What is Zostavax?
Single dose vaccine for herpes zoster. Recommended for adults >60, even if they have had a prior shingles episode. Contains a higher viral load that Varivax. Reduced risk of shingles by 50% in >60. Reduced by almost 70% in age group 50-59.
Histological scrapings of suspected VZV infection will show what?
Syncytial formation and intranuclear inclusions. Uses the Tzanck smear.
What is the key to VZV pathogenesis?
The ability of the virus to engage in syncytial formation. Fusion of virus infected host cells with neighboring cells enable evasion of neutralizing antibodies.
What is the treatment of VZV in healthy children?
The disease is allowed to run its course if the child has a healthy immune system.
What is the best way to prevent PHN?
The herpes zoster vaccine. Decreased incidence of PHN by 67%.
Other than Varizig, what is used to reduce the severity of a VZV infection, post-exposure?
The varicella vaccine. If used within 72 hours (possibly up to 5 days) of exposure. Guidelines state that, because not every known VZV exposure leads to VZV, the vaccine should be given even if 5 days have passed since the known VZV exposure, in order to induce future immunity.
How is chicken pox acquired?
Through inhalation of respiratory droplets.
What is Varivax?
Two dose live attenuated Oka strain VZV vaccine. Prevents VZV in 70-90% and reduces severity of VZV by 95%.
How many stages of viremia occur in primary VZV infection?
Two. Primary viremia - 5 days post infection Secondary viremia - about 11 days post infection
How does VZV spread within the body?
Virus is acquires through inhalation of respiratory droplets. These then enter the respiratory tract and make their way to the regional lymph nodes. The virus spreads from respiratory epithelial cells to T cells, which carry the virus to the skin.
How can an individual be tested for immunity to VZV?
Whole infected cell ELISA to look for antibodies from previous infection. Tests are not sensitive enough to detect immunity in all vaccinated individuals who never had VZV.
Is VZV enveloped?
Yes
Can a person get chicken pox more than once?
Yes, but it is very rare.
Is shingles contagious?
Yes, highly.
Is varicella zoster virus contagious before the appearance of the rash?
Yes, patients are contagious from 1-2 days before the rash appears until all of the lesions have scabbed over.
Can a person get shingles more than one?
Yes.
What type of genome does VZV have?
dsDNA, linear VZV has the smallest genome of the herpes viruses
