, colloquially known as '''shingles''', is the reactivation of
Varicella Zoster Virus , leading to a crop of painful blisters over the area of a
Dermatome . In
Italy and in
Malta , it is sometimes referred to as
St. Anthony's fire. It occurs very rarely in children and adults, but its incidence is high in the elderly (over 60), as well as in any age group of
Immunocompromised patients. It affects some 500,000 people per year in the United States. Treatment is generally with antiviral drugs such as
Aciclovir . Many patients develop a painful condition called
Postherpetic Neuralgia which is often difficult to manage.
In some patients, herpes zoster can reactivate subclinically with pain in a dermatomal distribution without rash. This condition is known as zoster sine herpete and may be more complicated, affecting multiple levels of the nervous system and causing multiple
Cranial neuropathies,
Polyneuritis ,
Myelitis , or
Aseptic Meningitis .
The word ''herpes'' comes from the
Greek word for ''
Snake ''; it is
Cognate with ''
Herpetology ''. Interestingly, the skin disease is also commonly known as "snake" in
Chinese .
Often,
Pain is the first symptom. This pain can be characterized as stinging, tingling, numbing, or throbbing, and can be pronounced with quick stabs of intensity. Then 2-3 crops of red lesions develop, which gradually turn into small
Blister s filled with
Serous Fluid . A general feeling of unwellness often occurs. In some cases, the rash does not form blisters, but has an appearance much like
Urticaria ("hives").
As long as the blisters have not dried out, HZ patients may transmit the virus to others. This could lead to
Chickenpox in people (mainly young children) who are not yet immune to this virus.
Shingles blisters are unusual in that they only appear on one side of the body. That is because the chickenpox virus can remain dormant for decades, and does so inside the
Spinal Column or a
Nerve Fiber . If it reactivates as shingles, it affects only a single nerve fiber, or ganglion, which can radiate to only one side of the body. The blisters therefore only affect one area of the body and do not cross the midline. They are most common on the torso, but can also appear on the face (where they are potentially hazardous to vision) or other parts of the body.
The diagnosis is visual — very few other diseases mimic herpes zoster. In case of doubt, fluid from a blister may be analysed in a
Medical Laboratory .
The causative agent for herpes zoster is
Varicella Zoster Virus (VZV). Most people are infected with this virus as a child, as it causes
Chickenpox . The body eliminates the virus from the system, but it remains dormant in the
Ganglia adjacent to the spinal cord (called the dorsal root ganglion) or the
Ganglion Semilunare (ganglion Gasseri) in the cranial base.
Generally, the
Immune System suppresses reactivation of the virus. In the elderly, whose immune response generally tends to deteriorate, as well as in those patients whose immune system is being suppressed, this process fails. (Some researchers speculate that
Sunburn and other, unrelated stresses that can affect the immune system may also lead to viral reactivation.) The virus starts replicating in the nerve cells, and newly formed viruses are carried down the
Axon s to the area of skin served by that ganglion (a
Dermatome ). Here, the virus causes local
Inflammation in the skin, with the formation of blisters.
The pain characteristic of herpes zoster is thought to be due to irritation of the sensory nerve fibers in which the virus reproduces.
Aciclovir (an
Antiviral Drug ) inhibits replication of the viral DNA, and is used both as
Prophylaxis (e.g. in patients with
AIDS ) and as therapy for herpes zoster. Other antivirals are
Valaciclovir and
Famciclovir .
Steroid s are often given in severe cases. During the acute phase oral aciclovir should be given five times daily for 7 to 10 days. Immunocompromised patients may respond best to intravenous aciclovir. In patients who are at high risk for recurrences, an oral dose of aciclovir, taken twice daily, is usually effective.
The long term complication
Postherpetic Neuralgia may cause persistent pain that lasts for years. Pain management is difficult as conventional analgesics may be ineffective. Alternative agents are often used, including
Tricyclic Antidepressant s (particularly
Amitriptyline ),
Anticonvulsant s (e.g.
Gabapentin , and/or topical
Capscaicin ).
A
Vaccine called live attenuated Oka/Merck VZV that has been developed by
Merck & Co. has proven successful in preventing half the cases of herpes zoster in a study of 38,000 people who received the vaccine. The vaccine also reduced by two-thirds the number of cases of postherpetic neuralgia (Oxman ''et al.'', 2005). However, prior to the vaccine, it has long been known that adults received natural immune boosting from contact with children infected with varicella. This helped to suppress the reactivation of herpes zoster. In Massachusetts, herpes zoster incidence increased 90%, from 2.77/1000 to 5.25/1000 in the period of increasing varicella vaccination 1999-2003 (Yih ''et al.'', 2005). The effectiveness of the varicella vaccine itself is dependent on this exogenous (outside) boosting mechanism. Thus, as natural cases of varicella decline, so has the effectiveness of the vaccine (Goldman, 2005).
Often the same treatment given to burn victims relieves the pain of shingles, including over-the-counter moist burn pads.
The rash and pain usually subside within 3 to 5 weeks. The most common complication of herpes zoster is
Postherpetic Neuralgia . Pain that persists for longer than one to three months after resolution of the rash is generally accepted as the sign of postherpetic neuralgia. Sometimes serious effects
including partial
Facial Paralysis (usually temporary), ear damage, or
Encephalitis may occur. Shingles on the upper half of the face (the first branch of the
Trigeminal Nerve ) may result in
Eye damage and require urgent ophthalmological assessment.
Ocular complications occur in approximately one half of patients with involvement of the ophthalmic division of the
Trigeminal Nerve . These complications include
Mucopurulent Conjunctivitis ,
Episcleritis ,
Keratitis and anterior
Uveitis . Cranial nerve
Palsies of the third, fourth and sixth
Cranial Nerve s may occur, affecting
Extraocular Motility .
Since shingles is a reactivation of a virus contracted previously—often decades earlier—it cannot be induced by exposure to another person with shingles or chickenpox. However, those with active blisters can spread chickenpox to others who have never had that condition and who have not been vaccinated against it.
