Herpes zoster, also commonly known as shingles, is a neurological disorder caused by the reactivation of varicella zoster virus (VZV), the same virus that causes chickenpox.
Based on recent research and publications, we estimate that there are over four million cases of shingles in the U.S., Europe and Japan each year, of which more than half occur in the U.S.
The symptoms associated with shingles generally include localized lesions and pain. In many cases the patient may first notice localized prodomal pain; however, the first recognizable symptom of shingles is generally lesions that will continue to form for a week or two. These lesions generally follow the path of nerves that emanate from the spinal cord around the torso (thoracic); however, the infection is also commonly found on the face, neck, lower back and in certain cases, systemically.
Within several weeks, the lesions in the infected areas will typically begin to heal, and these dermatological symptoms generally will resolve within a month or less. In rare instances, lesions may never appear, but pain will be present.
Reactivation of varicella zoster virus (VZV)
The pain associated with an episode of shingles is attributed to both the damage caused to the affected nerves by the replication of VZV and the inflammatory response associated with the infection.
Pain symptoms are commonly described as a burning sensation, with bouts of stabbing and shooting pain, often set off by contact with the infected area. The majority of shingles patients experience such pain for several weeks in connection with their active infection, referred to as acute pain. For many patients, shingles-associated pain does not resolve when the lesions heal and the inflammation subsides, but, rather, continues for months, or possibly years.
Persistent shingles-associated pain that lasts more than three to four weeks is referred to as sub-acute pain or neuralgia. Shingles-associated pain that persists more than three months is generally referred to as PHN, which is the most common and clinically relevant complication of shingles.
Approximately 15-20% of all shingles patients experience PHN, although the incidence of PHN is more prevalent in patients over 50 years of age. Previous studies have established that additional risk factors for PHN include greater acute pain intensity, severity of the dermatological symptoms or lesions, and the presence and greater severity of a painful prodromal preceding the lesions or rash.