Shingles

Herpes zoster (or simply zoster), commonly known as shingles and also known as zona, is a <a href="http://en.wikipedia.org/wiki/Viral_disease" title="Viral disease">viral disease</a> characterized by a <a href="http://en.wikipedia.org/wiki/Pain" title="Pain">painful</a> skin rash with <a href="http://en.wikipedia.org/wiki/Blister" title="Blister">blisters</a> in a limited area on one side of the body, often in a stripe. The initial infection with <a href="http://en.wikipedia.org/wiki/Varicella_zoster_virus" title="Varicella zoster virus">varicella zoster virus</a> (VZV) causes the acute (short-lived) illness <a href="http://en.wikipedia.org/wiki/Chickenpox" title="Chickenpox">chickenpox</a> which generally occurs in children and young people. Once an episode of chickenpox has resolved, the virus is not eliminated from the body but can go on to cause shingles—an illness with very different symptoms—often many years after the initial infection. Herpes zoster is not the same disease as <a href="http://en.wikipedia.org/wiki/Herpes_simplex" title="Herpes simplex">herpes simplex</a> despite the name similarity (both the varicella zoster virus and <a href="http://en.wikipedia.org/wiki/Herpes_simplex_virus" title="Herpes simplex virus">herpes simplex virus</a> belong to the same viral subfamily <a href="http://en.wikipedia.org/wiki/Alphaherpesvirinae" title="Alphaherpesvirinae">Alphaherpesvirinae</a>).

Varicella zoster virus can become <a href="http://en.wikipedia.org/wiki/Virus_latency" title="Virus latency">latent</a> in the <a href="http://en.wikipedia.org/wiki/Neuron" title="Neuron">nerve cell bodies</a> and less frequently in <a href="http://en.wikipedia.org/wiki/Satellite_cells" title="Satellite cells" class="mw-redirect">non-neuronal satellite cells</a> of <a href="http://en.wikipedia.org/wiki/Dorsal_root_ganglion" title="Dorsal root ganglion">dorsal root</a>, <a href="http://en.wikipedia.org/wiki/Cranial_nerves" title="Cranial nerves" class="mw-redirect">cranial nerve</a> or <a href="http://en.wikipedia.org/wiki/Autonomic_nervous_system" title="Autonomic nervous system">autonomic</a> <a href="http://en.wikipedia.org/wiki/Ganglion" title="Ganglion">ganglion</a>,<a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid12676845-0">[1]</a> without causing any <a href="http://en.wikipedia.org/wiki/Symptoms" title="Symptoms" class="mw-redirect">symptoms</a>.<a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid12211045-1">[2]</a> Years or decades after a chickenpox infection, the virus may break out of nerve cell bodies and travel down nerve <a href="http://en.wikipedia.org/wiki/Axon" title="Axon">axons</a> to cause viral infection of the skin in the region of the nerve. The virus may spread from one or more ganglia along nerves of an affected <a href="http://en.wikipedia.org/wiki/Segmentation_%28biology%29" title="Segmentation (biology)">segment</a> and infect the corresponding <a href="http://en.wikipedia.org/wiki/Dermatomic_area" title="Dermatomic area" class="mw-redirect">dermatome</a> (an area of skin supplied by one spinal nerve) causing a painful rash.<a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid1666443-2">[3]</a><a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid14583142-3">[4]</a> Although the rash usually heals within two to four weeks, some sufferers experience residual nerve pain for months or years, a condition called <a href="http://en.wikipedia.org/wiki/Postherpetic_neuralgia" title="Postherpetic neuralgia">postherpetic neuralgia</a>. Exactly how the virus remains latent in the body, and subsequently re-activates is not understood.<a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid12676845-0">[1]</a>

Throughout the world the <a href="http://en.wikipedia.org/wiki/Incidence_%28epidemiology%29" title="Incidence (epidemiology)">incidence rate</a> of herpes zoster every year ranges from 1.2 to 3.4 cases per 1,000 healthy individuals, increasing to 3.9–11.8 per year per 1,000 individuals among those older than 65 years.<a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid17143845-4">[5]</a><a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid7618983-5">[6]</a><a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid17939895-6">[7]</a> <a href="http://en.wikipedia.org/wiki/Antiviral_drug" title="Antiviral drug">Antiviral drug</a> treatment can reduce the severity and duration of herpes zoster if a seven-to-ten day course of these drugs is started within 72 hours of the appearance of the characteristic rash.<a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid17143845-4">[5]</a><a href="http://en.wikipedia.org/wiki/Shingles#cite_note-pmid18241179-7">[8]</a>