Chicken Pox (Varicella-zoster virus)

Chicken Pox (Varicella-zoster virus)

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Last edited and updated on: by Sagar Aryal

What is chickenpox?

  • Herpes virus (DNA)
  • Primary infection results in varicella (chickenpox)
  • Recurrent infection results in herpes zoster (shingles)
  • Short survival in the environment

Chicken Pox (Varicella-zoster virus)

Image Source: Wikipedia

Structure

  • VZV virions are spherical and 180–200 nm in diameter.
  • Their lipid envelope encloses the 100 nm nucleocapsid
  • Nucleocapsid has 162 hexameric and pentameric
  • capsomeres arranged in an icosahedral form.
  • Its DNA is a single, linear, double-stranded molecule, 125,000 nt long.
  • The capsid is surrounded by loosely associated proteins known collectively as the tegument; many of these proteins play critical roles in initiating the process of virus reproduction in the infected cell.
  • The tegument is in turn covered by a lipid envelope studded with glycoproteins that are displayed on the exterior of the virion, each approximately 8 nm long.

Genome

  • The genome was first sequenced in 1986. It is a linear duplex DNA molecule, a laboratory strain has 124,884 base pairs.
  • The varicella-zoster virus (VZV) genome contains at least 70 genes

Transmission

Chickenpox is a highly contagious disease. It is transmitted from person to person by direct contact (touching the rash), droplet or air born spread (coughing and sneezing) of vesicle fluid or secretions of the respiratory tract of cases or of vesicle fluid of patients with herpes zoster.

Pathogenesis

Day 0 – 3 Infection of conjunctivae and/or mucosa of the upper respiratory tract.

Viral replication in regional lymph  nodes

Day 4 – 6 Primary  Viremia

Viral replication in the liver, spleen,  and other organs

Days 10 – 12 Secondary Viremia
Day 14 Infection of skin and appearance of  vesicular rash

Sign and  Symptoms

The early symptoms of chickenpox may include cold symptoms, fever, abdominal pain, headaches and a general feeling of illness. These can come with a rash or a day or two before it. The fever may be high for the first few days.

Laboratory Diagnosis

  • Laboratory diagnosis is not routinely required
  • Useful if confirmation of the diagnosis or determination of susceptibility is necessary
  • A most frequent source of isolation is vesicular fluid
  • Stained smears from vesicular scrapings (Tzanck Smear).
  • Serology Tests for Varicella IgM antibody
  • ELISA and Latex Agglutination (LA) useful in screening for varicella immunity

Treating Chicken Pox with Scientific Medicine 

  • Zyrtec
  • Benadryl
  • Tylenol
  • Claritin
  • Calamine Lotion

Epidemiology

With a 2013 article reporting an incidence rate of 1.02 cases per 100,000 inhabitants in Switzerland, and an annual incidence rate of 1.8 cases per 100,000 inhabitants in Sweden.

Congenital Varicella Syndrome

  • Results from maternal infection during pregnancy
  • Period of risk may extend through the first 20 weeks of pregnancy
  • Atrophy of extremity with skin scarring, low birth weight, eye and neurologic abnormalities
  • The risk appears to be small (<2%)

Complications Result From Varicella

  • The most common complications are:
  • Bacterial infections of the skin and soft tissues in children
  • Septicemia
  • Toxic Shock Syndrome
  • Necrotizing Fascitis
  • Osteomyelitis
  • Bacterial pneumonia
  • Septic arthritis.

References

  1. https://www.webmd.com/children/what-is-chickenpox
  2. https://www.medicalnewstoday.com/articles/239450.php
  3. https://en.wikipedia.org/wiki/Chickenpox
  4. https://www.cdc.gov/chickenpox/index.html

Chicken Pox (Varicella-zoster virus)

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