What is Shingles?

Scientists believe that in the original battle with the chickenpox virus some of the virus particles leave the skin blisters and move into the nervous system. There the viruses settle down in an inactive (latent) form inside specific nerve cells (neurons) that relay information to the brain about what your body is sensing whether your skin feels hot or cold, whether you've been touched or feel pain. These lie in clusters (ganglia) adjacent to the spinal cord and brain and are one type of sensory neurons.

When the chickenpox virus reactivates, the virus moves down the long nerve fibers that extend from the sensory cell bodies to the skin. The viruses multiply, the telltale rash erupts, and the person now has herpes zoster, or shingles. With shingles, the nervous system is more deeply involved than it was during the bout with chickenpox, and the symptoms are often more complex and severe.

The virus responsible for shingles and chickenpox belongs to a group of viruses called herpesviruses. This group includes the herpes simplex virus that causes cold sores, fever blisters, mononucleosis, genital herpes a sexually transmitted disease, and Epstein-Barr virus involved in infectious mononucleosis. Like the shingles-causing virus, many other herpesviruses can take refuge in the nervous system after an individual has suffered an initial infection. These viruses may remain latent for years, then travel down nerve cell fibers to cause a renewed infection.

The varicella-zoster virus looks as though it were designed by a mathematician. It is a microscopic sphere encasing a 20-sided geometric figure called an icosahedron. Inside the icosahedron is the genetic material of the virus, deoxyribonucleic acid (DNA). When activated, the virus reproduces inside the nucleus of an infected cell. It acquires its spherical wrapping as it buds through the nuclear membrane.

Back to Your Guide to Shingles
Reviewed by Michael W. Smith, MD, June 2005.

SOURCE: National Institute of Neurological Disorders and Stroke, National Institutes of Health, U.S. Department of Health and Human Services. http://www.ninds.nih.gov/health_and_medical/pubs/shingles.htm