The strains of the herpes virus that affect humans share a common phenomenon called "latency": after the initial infection, the virus retreats to the immune system where it becomes dormant, or inactive, for a period of time. At times, for reasons not fully understood, the virus can reactivate. When it does, it travels from the nervous system back to the skin, though depending upon the viral strain, recurrent infections do not always affect the same site of the first infection.
Varicella-Zoster Virus
Varicella-zoster virus (VZV) is the strain of herpes virus that causes chickenpox, a highly contagious disease that causes a wide-spread, itchy body rash characterized by fluid-filled blisters. The Centers for Disease Control and Prevention (CDC) estimate that the majority of cases of chickenpox in unvaccinated people will cause between 250 and 500 blisters. Before the development of a vaccine, most cases of chickenpox occurred in people under the age of 15. In 2006, the Advisory Committee on Immunization Practices (ACIP) recommended a two-dose vaccine for all children. Of those who have only received one dose of the vaccine, 15 to 20 percent will still develop the disease, though the CDC reports that their symptoms will usually be mild. Once a person recovers from chickenpox, it is highly unlikely that a second outbreak will occur. Instead, VZV can cause a different type of outbreak.
Herpes Zoster
Herpes zoster, or shingles, is a reactivation of VZV in a person who has already had chickenpox, or who received the chickenpox vaccine. The National Institute of Neurological Disorders and Stroke (NINDS) reports that "varicella" is derived from the Latin word "variola," which is the name given to smallpox, a deadly disease that which can resemble chickenpox. "Zoster" is the Greek word for "girdle." "Shingles" is derived from the Latin word "cingulum," which also means "girdle." Unlike chickenpox, when a VZV reactivation occurs and causes shingles, the blisters tend to erupt in a girdle-like band on one side of the torso. Less often, the band can appear on the neck or face. The first symptom of shingles is often a tingling sensation at the site where the outbreak will occur. Within several days to a week, blisters will appear at the site. In some instances, the symptoms will be so mild that they will not be noticed, or properly diagnosed. The name given to cases without lesions is "zoster sine herpete." In many cases, however, pain will accompany a shingles outbreak. The pain can range from mild to intense. NINDS reports that the rash usually subsides within a few weeks in healthy people, without leaving scars.
Complications
In some cases of shingles, the rash heals and fades, but pain remains. This is called "postherpatic neuralgia." The University of Chicago's Peripheral Neuropathy Center reports that this pain can last from months to years after the rash has faded. The most severe cases, according to NINDS, can cause weigh loss, insomnia and depression.
Opthalmic shingles is another complication that can occur when the shingles outbreak occurs around or near the eye. When the eye becomes involved, pain, eye infections, vision impairment and even blindness become possibilities. If shingles occurs in or near to the ear, Ramsay-Hunt syndrome can result. Symptoms can include hearing loss, problems with balance and muscle damage on the affected side of the face.
