Shingles

Herpes zoster, colloquially known as shingles, is the reactivation of varicella zoster virus, leading to a crop of painful blisters over the area of a dermatome. 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 acyclovir. 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 came from Greek, which is cognate with serpent and, as can be expected, herpetology. Interestingly, the skin disease is also commonly known as "snake" in Chinese.

Signs and symptoms
 
Shingles on the forearmOften, 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 blisters filled with serous fluid. A general feeling of unwellness often occurs.

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.

Diagnosis
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.

Therapy
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. Steroids are often given in severe cases.

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 antidepressants (particularly amitriptyline), anticonvulsants (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.

Prognosis
The rash and pain usually subside within 3 to 5 weeks. The most common chronic 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 nerves 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.