ÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝ Varicella

 

The Virus:

…        Varicella zoster virus (VZV) causes chicken pox, member of the herpes virus group

…        Common to most people in temperate climates in their childhoodÝ

…        It is capable of persisting as a latent infection after primary infection eventually recurring as the disease known as shingles (herpes zoster)

…        Shingles usually occurs in older people due to decreased immunityÝ

…        The virus has short survival outside of the hostÝ

…        Once someone has recovered from the primary infection he or she generally has lifetime immunity

Immune response to virus:

Cell-mediated immunity:

…        The structural and regulatory proteins of VZV are recognized by T lymphocytes that produce Th1 cytokines such as IL-2 and IFN-gamma.Ý

…        People with diminished CMI tend to be more susceptible to shingles

…        The T lymphocyte response occurs within days after onset of typical rashes due to the virusÝ

…        Tests show this response is positive for years after infection.

Serum IgG:

…        Within four days after onset of rash and other symptoms of chicken pox, patients have a strong serum IgG response that can last up to 6-8 months and even be positive for years

Serum IgA:

…        Detected within 3-4 days after onset of rashes, serum IgA tends to decline more quickly than IgG.Ý

…        Quantities of nasopharyngeal IgA are also detected.

 

Brief Pathogenesis/Clinical Features:

…        Virus enters a host through the respiratory tract and conjunctiva

…        It replicates at the site of entry, initiating a primary viremia 4-6 days after infection

…        The virus is disseminated to the liver, spleen, sensory ganglia and other locations where it then begins to replicate in the visceraÝ

…        The secondary viremia causes the recognizable infection of the skinÝ

…        Lesions will form on all parts of the skin and in mucous membranes

…        Hosts are generally most contagious two days prior to the onset of rashes up until a week after the outbreak, once new lesions are no longer developingÝ

adults who develop chicken pox tend to have worse symptoms than children, with rashes often accompanied by fever and malaise