Medical Health Encyclopedia

Herpes Zoster (Shingles). The virus also travels to nerve cells called dorsal root ganglia. These are bundles of nerves that transmit sensory information from the skin to the brain. Here, the virus has properties that allow it to hide from the immune system for years, often for a lifetime. This inactivity is called latency.

Click the icon to see an image of shingles.

If the virus becomes active after being latent, it causes the disorder known as shingles. The virus in this later form is referred to as herpes zoster. The virus spreads in the ganglion and to the nerves connecting to it. Nerves most often affected are those in the face or the trunk. The virus, however, can also spread to the spinal cord and into the bloodstream.

It is not clear why the virus reactivates in some people and not in others. In many cases, the immune system has become impaired or suppressed from certain conditions such as AIDS or other immunodeficient diseases or from certain cancers or drugs that suppress the immune system. Aging itself may increase the risk for shingles.

Other Herpes Viruses

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The varicella-zoster virus belongs to a group of herpes viruses that includes seven human viruses (it also includes animal viruses as well). Herpes viruses are similar in shape and size and reproduce within the structure of a cell. The particular cell depends upon the specific virus. The human herpes viruses are:

• Herpes Simplex virus (the most common).
• Varicella-zoster virus (VZV).
• Cytomegalovirus (CMV).
• Epstein-Barre virus (causes mononucleosis).
• Human herpesvirus type 6 (causes roseola).
• Human herpesvirus type 7 (HHV-7).

All herpes viruses share some common properties, including a pattern of active symptoms followed by latent inactive periods that can last for months, years, or even for a lifetime.