Friday, December 12

Is herpes zoster contagious? - Herpes zoster causes and transmission

   ›      ›   Herpes zoster causes.
Herpes zoster, also known as shingles, zona or zoster is a contagious skin infection caused by the varicella-zoster virus (VZV or human herpesvirus type 3).
The primary infection caused by the VSV is the chickenpox (varicella). Varicella usually occurs in the childhood manifesting as widespread vesicular rash. Later on reactivated virus causes herpes zoster. The zoster rash appears on the respective dermatome, i.e., the area of skin to which the affected spinal nerve is supplying.

Herpes zoster is contagious

The virus after causing highly contagious chickenpox enters the nervous system and remains for life in a dormant condition in the sensory dorsal root ganglia or cranial nerve ganglia. The affected individuals develop partial immunity and the virus is not totally eliminated by the immune system. The virus may get reactivated anytime and cause zoster in the affected person and cause varicella in others coming under direct contact with lesions.

Cause of herpes zoster

After years of dormancy, VZV may get reactivated in some persons and cause vesicles. The exact cause of relapse to active phase is not known. However the main triggering factor may be immunodeficiency and immunosuppression. After activation, the virus particles move down the nerve and reach the area of skin supplied by the nerve and cause blisters. The occurrence of this contagious disease is more common in old age. Before the advent of vaccination for VZV, most of the adults might have contracted chickenpox in their childhood. Though the virus is dormant in them, they are carriers of the virus.
diagram showing the stages in the course of herpes zoster infection
course of herpes zoster infection
Stages in the progression of herpes zoster are given in the above image.
shingles on neck
herpes zoster on neck

  • 1.Initially there is itching and burning sensation followed by the appearance of a cluster of small bumps.
  • 2.These swellings turns into small blisters.
  • 3.The blisters fill with lymph and break open exuding the contents. They may get infected and pus may form.
  • 4.The blisters start healing, crust over and disappear.
  • 5.Postherpetic neuralgia may occur due to nerve damage and persist for sometime after healing.

Herpes zoster transmission

The transmission of either chickenpox or zoster is by direct or indirect contact with fluids exuding from the blisters or with crust formed during healing. The varicella may also get transmitted by breathing infected coughed droplets. Transmission of the infection to others occurs when the virus gets reactivated. Transmission of the VZV to those who did not have chickenpox earlier in their life will cause chickenpox in them.
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Transmission of this contagious disease commonly occurs from affected grandparents to unimmunized grandchildren resulting in varicella.

Risk factors

  • The occurrence of zoster is most common after 50 years of age. The risk of developing the contagious blisters increases with the increase in age.
  • Patients taking high-dose corticosteroids for some other health condition are at risk.
  • Patients taking immunosuppressant drugs for some other condition like organ transplant are also at risk.
  • Patient affected by cancers, AIDS and autoimmune diseases are at risk.
  • Patients undergoing chemotherapy or generalised radiotherapy are at the risk of reactivated herpes zoster.

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Reference:
1.Zostavax (Herpes Zoster Vaccine) Questions and Answers (FDA)
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1.Image source: http://en.wikipedia.org/wiki/File:A_Course_of_Shingles_diagram.png
Author: FDA | License: public domain.
2.Image source: http://en.wikipedia.org/wiki/File:Herpes_zoster_neck.png
Author: John Pozniak | License: CC BY-SA 3.0
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