What is shingles (herpes zoster)?
Herpes zoster, commonly known as shingles, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe or dermatome. The initial infection with varicella zoster virus causes chickenpox which generally occurs in children and young people. Once an episode of chickenpox has resolved, the virus lies dormant in the body and can go on to cause shingles infection years later.
Antiviral drug treatment can reduce the severity and duration of herpes zoster if a seven- to ten-day course of these drugs is started within 72 hours of the appearance of the rash.
How does herpes zoster develop?
The earliest symptoms of herpes zoster, which include headache, fever, and malaise, are commonly followed by sensations of burning pain, itching, oversensitivity, or pins and needles feeling, tingling, pricking, or numbness. The pain may be mild to extreme in the affected area, and can have intervals of quick stabs of agonizing pain.
In most cases, after 1–2 days, the initial phase is followed by the appearance of the characteristic skin rash. The pain and rash most commonly occur on the torso, but can appear on the face, eyes or other parts of the body. At first, the rash appears similar to the first appearance of hives; however, unlike hives, herpes zoster causes skin changes normally resulting in a stripe or belt-like pattern that is limited to one side of the body and does not cross the midline. Later, the rash forms small fluid filled blisters, as the fever and general malaise continue. The painful vesicles eventually become cloudy or darkened as they fill with blood and crust over within seven to ten days. Usually the crusts fall off and the skin heals, but sometimes after severe blistering, scarring and discolored skin remain.
Who gets herpes zoster?
Herpes zoster occurs only in people who have had chickenpox, and although it can occur at any age, the majority of sufferers are more than 50 years old. The disease results from the virus reactivating in a single sensory ganglion. Repeated attacks of herpes zoster are rare, and it is extremely rare for patients to suffer more than three recurrences.
What causes herpes zoster?
Unless the immune system is compromised, it suppresses reactivation of the virus and prevents herpes zoster. Why this suppression sometimes fails is poorly understood, but herpes zoster is more likely to occur in people whose immune system is impaired due to aging, immunosuppressive therapy, psychological stress, or other factors. Upon reactivation, the virus replicates in the nerve cells, and virions shed from the cells are carried down the axons to the area of skin served by that ganglion. In the skin, the virus causes local inflammation and blisters. The short and long term pain caused by herpes zoster comes from the widespread growth of the virus in the infected nerves, which causes inflammation.
The symptoms of herpes zoster cannot be transmitted to another person. However, during the blister phase, direct contact with the rash can spread varicella zoster virus to a person who has no immunity to it. This newly-infected individual may then develop chickenpox, but will not immediately develop shingles. Until the rash has developed crusts, a person is extremely contagious but is not infectious before blisters appear, or after the rash has disappeared.
How is herpes zoster treated?
A live vaccine for varicella zoster virus exists, marketed as Zostavax. In October 2007 the vaccine was officially recommended in the U.S. for healthy adults aged 60 and over. Adults also receive an immune boost from contact with children infected with varicella, a boosting method that prevents about a quarter of herpes zoster cases among unvaccinated adults, but which is becoming less common in the U.S. now that children are routinely vaccinated against varicella.
Patients with mild to moderate pain can be treated with over-the-counter analgesics. Topical lotions can be used on help soothe the rash or blisters. Occasionally, severe pain may require a stronger medication. Topical lidocaine and nerve blocks may also reduce pain.
Antiviral drugs inhibit varicella zoster virus replication and reduce the severity and duration of herpes zoster with minimal side effects. Of these drugs, acyclovir has been the standard treatment, but the new drugs Valacyclovir (Valtrex) and Famciclovir (Famvir) demonstrate similar or superior efficacy and good safety and tolerability. The drugs are used both as prophylaxis and as therapy during the acute phase. Antiviral treatment is recommended for all immunocompetent individuals with herpes zoster over 50 years old, preferably given within 72 hours of the appearance of the rash. Complications in immunocompromised individuals with herpes zoster may be reduced with intravenous acyclovir.
Although herpes zoster typically resolves within 2 weeks, certain complications may arise such as secondary bacterial infection, motor involvement including weakness, eye involvement should be treated early and aggressively as it may lead to blindness, trigeminal nerve involvement, Involvement of the tip of the nose in the zoster rash is a strong predictor of herpes ophthalmicus, or shingles involving the eye.The rash and pain usually subside within three to five weeks, but about one in five patients develop a painful condition called postherpetic neuralgia, which is often difficult to manage and may result in pain for many months after the rash is resolved.