Acute herpes zoster, commonly called shingles, is an acute infectious
viral disease that primarily affects the posterior spinal root ganglia
of the spinal nerves. A single posterior spinal root ganglion or
a small number of adjacent ones may be affected, usually on the
same side. The corresponding ganglia of the cranial nerves also
may be involved similarly. The causative virus, varicella-zoster,
belongs to a DNA group of viruses that is host specific. The same
virus produces chickenpox or varicella in children and young people.
Herpes zoster most frequently occurs in adults who previously
have had chickenpox. It is thought that the virus remains dormant
in the dorsal root ganglia until, many years later, it is reactivated and
produces herpes zoster. The decrease in immunity that permits the
reactivation may be caused by infection or malignancy, or it may
occur in the iatrogenically immunosuppressed patient. The impact
of stress on varicella-zoster virus has not been well studied, but
major depression has been associated with markedly decreased varicella-zoster
virus–specific cellular immunity.1 Patients
experiencing stress during a zoster episode are more likely to have
more severe pain, increasing their risk of postherpetic neuralgia.2 Patients
with herpes zoster occasionally relate a history of recent contact
with the virus exogenously; but it is rare, if ever, that an infection
so develops. The incidence of herpes zoster does not increase during
seasonal chickenpox epidemics.
It is thought that, after the virus multiplies in the dorsal
root ganglion, it is transported along the sensory nerves to the
nerve endings, where the lesions are formed. In the immunocompetent patient,
the disease is confined to a local distribution because there is
a rapid mobilization of defense mechanisms.
Although the posterior root ganglia of the spinal and cranial
nerves are involved most commonly, any part of the central nervous
system can be affected. For example, the anterior motor horn may be
involved, or the patient may have myelitis or encephalomyelitis.
In rare cases, only the sympathetic ganglia are affected, resulting
in a syndrome resembling reflex sympathetic dystrophy.
The location of the herpes zoster infection may be determined
by the site of a primary inflammatory disease, malignancy, or trauma.
Patients with neoplasms, especially lymphomas, are more susceptible
to herpes zoster. This high incidence may be the result of recent
radiation of affected nodes, advanced disease, and possible splenectomy.
Other associated diseases include meningitis, spinal cord tumors,
anterior poliomyelitis, syringomyelia, tabes dorsalis, intoxication
from arsenicals or carbon monoxide, and malignant neoplasms such
as breast, lung, or gastrointestinal tumors.
Estimates of the incidence of herpes zoster in the U.S. population
indicate an approximate 64% increase in the general population
over the past 30 years, to approximately 215 cases per 100,000 person
years.3 Men are affected more frequently than women.
African Americans 65 years of age or older are significantly less