Herpes zoster (or zoster), is known as shingles or zona and is a viral disease characterized by painful skin rash with blisters in a limited area on one side of the body. Initial infection causes chickenpox. Once chickenpox is over the virus remains in the body and can cause shingles. It can become latent in the nerve cell bodies and sometimes in the dorsal root, cranial nerve, or autonomic ganglion. Years after initial infection, another breakout can cause a painful rash. The rash usually heals within two to four weeks although it can persist for months or years.
Worldwide incidence rate ranges from 1.2 to 3.4 cases per 1,000 healthy individuals amongst those older than 65 years. Antiviral drugs are capable of reducing the severity and duration of herpes zoster.
Although similar in name herpes zoster is no the same as herpes simplex though they are both part of the same viral subfamily. Early symptoms include headache, fever, and malaise which are nonspecific and often lead to misdiagnosis. These symptoms are commonly followed by itching, hyperesthesia, and paresthesia. Pain may be mild to extreme and accompanied with sensations that are often described as stinging, tingling, aching, numbing, or throbbing, interspersed with stabs of agonizing pain. Rash most often occurs on the torso but can appear on the face, eyes, or other parts of the body. These rashes, unlike hives, can cause dermatome. The rash eventually becomes vesicular and forms small blisters.
Rarely symptoms may include conjunctivitis, keratitis, uveitis, and optic nerve palsies that can cause chronic ocular inflammation, loss of vision, and debilitating pain. Ramsay Hunt syndrome II, involves the ear, and is though to result from the virus spreading form the facial nerve to the vestibulocochlear nerve.
Causative agent for herpes zoster is varicella zoster virus which is a double-stranded DNA virus related to the Herpes simplex virus group. Zoster occurs primarily in people of more than 50 years old. The immune system suppresses reactivation of the virus. Why the suppression fails is not very well understood. It cannot be transmitted to another person except during the blister phase where it can spread to people without immunity. Anyone infected that doesn’t have previous immunity will develop chickenpox but not necessarily shingles.
Laboratory test are used to diagnose zoster. The most popular test will detect VZV IgM antibody in blood.
Zostavax is a live vaccine for VZV. In a study of 38,000 adults the vaccine prevented half the cases of herpes zoster and reduced the number of post herpetic neuralgia by two-thirds. Treatment aims to limit severity and duration of pain and to reduce complications. Analgesics can be used to treat mild to moderate pain. Severe pain may sometimes require opioid medication, such as morphine. Despite lack of effective evidence orally administered corticosteroids are used in treatment of the infection.
Rash and pain are usually gone within three to five weeks. However, some people develop a painful condition called post-herpetic neuralgia. Ear damage, facial paralysis, and encephalitis can also occur.
Generally herpes zoster doesn’t occur seasonally and does not occur in epidemics. A study shows that people with a relative who had shingles is twice as likely to develop it themselves. The fact that chickenpox and herpes zoster were caused by the same virus was noticed at the beginning of the 20th century. Thomas Huckle Weller confirmed this in 1953 when he isolated the virus in cell cultures. The disease was considered benign until the 1940s.