There are 130,000 cases of shingles in Canada every year. Shingles or herpes zoster (HZ) is a viral disease that first manifests as pain, itching or tingling in an area of skin on one side of the body or face. Then a painful blistering rash develops in that same skin area, which can take 2-4 weeks to heal. Of these cases, 13% result in post-herpetic neuralgia (PHN), chronic severe pain that persists after the rash has cleared. This translates into 17,000 cases of PHN annually. As many as 70% of these patients will be adults over age 60.
A childhood connection
Early in the 20th century, researchers discovered that chickenpox and shingles were caused by the same virus. The chicken pox virus can lie dormant in the body for years – decades – and reappear with reactivation of the virus as shingles.
Advancing age (over 50) and a waning immune system are among the primary risk factors for shingles. There’s a race between reactivation of the virus and the immune system trying to control it. The immune system can also diminish as a result of conditions such as HIV, malignancies and immunosuppressive therapies. As a result, the primary virus can reactivate and replicate where it lies dormant. The virus spreads along a nerve root, causing inflammation and death of some of our nerve cells, leading to the symptomatic pain and rash seen with shingles.
In Canada, 90-95% of people are infected with the chicken pox varicella zoster virus by age 12 (prior to the varicella vaccine program), and approximately 20-30% of Canadians will develop shingles at some point in their lives.
Complications from shingles, including PHN, may occur in up to 40% of cases. Symptoms of PHN include:
- Constant / intermittent pain
- Allodynia: pain evoked by a mild normal stimulus – heat, cold or tactile
- Hyperalgesia: severe pain
- Intense itching.
Treatment of shingles and PHN is complex and sometimes unsuccessful in alleviating the symptoms. Prescription anti-viral medications may be beneficial in treating shingles if started within 72 hours of the onset of initial symptoms. Other complications from shingles include: ocular complications of ophthalmic zoster; scarring on the skin from the rash; and bacterial super-infection. See your doctor immediately to begin treatment where appropriate.
New vaccine prevention
In 2009, Canadians will have access to a vaccine made of live varicella virus. Clinical studies of those age 60 and over show this vaccine successfully reduced the incidence of shingles by 51%, and diminished the severity by 61% in those who contracted shingles. PHN was significantly reduced by two-thirds.
With increased risk of shingles in our aging population, primary vaccine prevention for those 60 and older is a worthwhile and effective strategy. H&L