Chickenpox (Varicella) and Shingles (Herpes Zoster)

Chickenpox (varicella) is a very highly contagious disease of the skin primarily of children two to seven years of age. Humans are the reservoir and the source for this virus, which is acquired by droplet inhalation into the respiratory system.

The virus is very infectious, with secondary infection rates in susceptible household contacts of 65 to 86%. In the pre-vaccine age, approx 4 million cases of chickenpox Occured annually in the US, resulting in approximately 11,000 hospitalizations band 100 to 150 deaths.

The virus is the enveloped, double-stranded (ds) DNA varicella-zoster virus a member of the family Herpesviridae. The virus produces a minimum of six glycoproteins that play a role in viral attachment to specific receptors on respiratory epithelial cells.

The  incubation period of 10 to 23 days, small vesicles appear on the face or upper trunk, fill with pus, rupture, and become covered by blisters. Healing of the vesicles occurs in about 10 days. During this time, intense itching often occurs.

• Day 1: Infection of conjunctiva or mucosa of upper respiratory tract. Viral replication in regional lymph nodes.
• Day 4-6: Primary viremia in the bloodstream. Viral replication in the liver and the spleen.
• Day 10: Skin infection and appearance of vesicular rash.

Laboratory testing for VZV is not normally required, as the diagnosis of chickenpox is typically made by clinical assessment. Laboratory confirmation is recommended, though, to confirm the diagnosis of severe or unusual cases of chickenpox. The introduction of the attenuated varicella vaccine in the 1990s has drastically reduced the incidence of chickenpox.

However because fewer cases are seen, the likelihood of misdiagnosis is increased. Furthermore, in persons who have previously received varicella vaccination, chickenpox is still possible, as immunity wanes. In these individuals, mild or atypical chickenpox symptoms may occur, posing particular challenges for clinical diagnosis.

Chickenpox infection can be shortened with the drug acyclovir. The vaccine is recommended for ages twelve months to twelve years and can be administered separately or as a combined measles, mumps, rubella (MMR) and varicella (MMVR) vaccine.

Individuals who get over from this disease are subsequently resistence to this disease; however, they are not free of the virus, as viral DNA resides in a dormant (latent) state within the nuclei of cranial nerves and sensory neurons in the dorsal root ganglia.

When the infected person becomes immunocompromised by these factors as age, cancers, organ transplants, AIDS, or psychological or physiological stress, the viruses may become activated.

They migrate down sensory nerves, initiate viral replication, and produce painful vesicles due to nerve damage. This syndrome is called postherpetic neuralgia. To manage the intense pain, corticosteroids or the drug gabapentin can be prescribed. The reactivated form of chickenpox is called shingles (herpes zoster). Most cases occur in people over fifty years of age.

Except for the pain of postherpetic neuralgia, shingles doesn’t require specific therapy; however, in immunocompromised individuals, acyclovir, valacyclovir, vidarabine, or famciclovir are recommended.

The U.S. Food and Drug Administration (FDA) has licensed a vaccine for shingles (Zostavax) for people fifty years and older. The Centers for Disease Control and Prevention (CDC) estimates that one in three people will get shingles. Cases more than 1 million of herpes zoster occurs annually in the US, with 50% of these in people over the age of sixty.

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Reference and Sources

• 1% – https://en.wikipedia.org/wiki/Varicella_zoster_virus
• 1% – https://4dtraveler.net/tag/crisis/page/8/
• 1% – https://www.thefreelibrary.com/Chapter+7+Viral+zoonoses.-a0183367857
• 2% – https://quizlet.com/87463563/last-micro-test-flash-cards/
• 2% – https://www.slideshare.net/KomalSah/chickenpoxmeaslessmall-poxrubella
• 2% – https://dph.georgia.gov/document/document/gdph-chickenpox-outbreak-protocol/download
• 1% – https://www.researchgate.net/publication/5575598_Varicella _and_the_pregnant _woman _Prevention_and_management

Also Read:

• Cold sores : Introduction, Entry, Symptoms, Diagnosis and Cure
• Second Golden Age of Microbiology
• Nosocomial Infection: Introduction, Source, Control and Prevention
• Nosocomial Infection: Introduction, Source, Control and Prevention
• Third Golden Age of Microbiology
• Antiviral Drugs