What Are the Causes of Shingles?
There is only one cause of
shingles (also known as
herpes zoster). The cause of shingles is a reinfection with the varicella-zoster virus. The varicella-zoster virus that causes shingles is the same virus that causes
chickenpox. The infection with this virus just tends to occur during different decades of a person's life.
The Varicella-Zoster Virus - - The "Cause of Shingles"
Varicella-zoster is part of the herpesvirus family. This group of viruses includes the herpes simplex virus (HSV) that causes
cold sores,
fever blisters,
genital herpes (a sexually transmitted disease), and the Epstein-Barr virus involved in infectious
mononucleosis.
As early as 1909, a German scientist suspected that the viruses causing chickenpox and shingles were one and the same. In the 1920s and 1930s, the case was strengthened. As part of an experiment, children were inoculated with fluid from the lesions of patients with shingles. Within two weeks, about half the children came down with chickenpox. Finally, in 1958, detailed analyses of the viruses taken from patients with either chickenpox or shingles confirmed that the viruses were identical.
So how does the same virus that causes chickenpox also cause shingles? To understand this, it may be helpful to understand the "reactivation" of the varicella-zoster virus.
Reactivation of the Shingles Virus Causes Shingles
After an attack of chickenpox, the varicella-zoster virus moves up into the nerves where it settles down in an inactive form (known as a latent form). It "lies down" inside specific nerve cells (neurons) that relay information to the brain about what your body is sensing -- such as whether your skin feels hot or cold, whether you've been touched, or whether you're feeling feel pain. These nerve cells lie in clusters (ganglia) adjacent to the spinal cord and brain, and are one type of sensory neurons.
As we get older, it is possible for the varicella-zoster virus to "come alive." When this happens, the shingle virus "reactivates" and then moves down the nerves to cause the
symptoms of shingles. Research scientists are still trying to understand why this happens and why it happens in some people and not in others.
Although shingles is most common in people over age 50, if you have had chickenpox or the
chickenpox vaccine, you are at risk for developing shingles. Shingles disease is also more common in people with weakened immune systems from
HIV infection, chemotherapy or radiation treatment, transplant operations, and stress.
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