Shingles eventually affects about 25 percent of the population, according to the National Institute of Neurological Disorders and Stroke, most after the age of 40. People with medical conditions---especially those that affect the immune system---are more likely to develop the disease than people without such problems. Unfortunately, the vaccine that prevents shingles---Zostavax---is not approved for many people with medical problems.
Mechanism
In the May 2010 edition of the "Journal of Clinical Virology," Columbia University pediatrician Anne A. Gershon explains that the body never completely clears the varicella-zoster virus that causes chicken pox. Instead, the virus lies dormant in the roots of spinal and, sometimes, cranial nerves. When the immune system is distracted by any medical condition or becomes less effective due to a medical condition or drug that specifically affects the immune system, the virus switches from a dormant state to an active state, resulting in shingles.
Risk Factors
Anyone can develop shingles, however some people are more susceptible than others. According to Gershon, medical conditions that increase the risk of developing shingles include AIDS, cancer---especially immune system cancers such as leukemia or lymphoma, diabetes, psychological stress and physical injury. People who use immune-suppressing drugs like prednisone also face increased risk, Gershon notes.
Precautions
According to Gershon, all people with shingles can spread the virus through contact with lesions or contact with objects directly exposed to lesions. Some people who have a medical condition with shingles may also be able to spread the virus through breath or saliva. As a result, the Centers for Disease Control and Prevention recommends that people who have not already experienced or been vaccinated against chicken pox wear a face mask with a rating of "N95" or higher when interacting with shingles patients who have AIDS or exhibit a rash that covers the entire body.
Clinical Features
Shingles causes a painful, blistering rash and, sometimes, a flu-like illness. People with medical conditions, according to University of Alabama Professor of Infectious Diseases Richard J. Whitley in the 2008 edition of "Harrison's Principles of Internal Medicine," may develop more blisters, distributed over a wider surface area of the body. Rashes are most severe, says Whitely, among people with AIDS, leukemia, lymphoma and those who take immunosuppressive drugs such as prednisone. Symptoms also last longer, says Whitley, and sometimes recur among these patients, although recurrent shingles is otherwise uncommon.
Treatment
Although shingles usually resolves without treatment, NINDS recommends prescription antiviral drugs such as acyclovir, valacyclovir and famciclovir to reduce the severity and duration of symptoms, as well as the risk of shingles-related complications. Patients who take medications for other conditions---especially amphotericin B, aminoglycosides, vancomycin, cyclosporine and aspirin or other non-steroidal anti-inflammatories--may require a reduced dose or additional tests to monitor for side effects.
References
- National Institute of Neurological Disorders and Stroke: Shingles: Hope Through Research
- "Journal of Clinical Virology"; Advances in the Understanding and Pathology of Herpes Zoster: A.A. Gershon et al.; May 2010
- "Harrison's Principles of Internal Medicine, 17th Edition"; A.S. Fauci et al.; 2008
- Centers for Disease Control and Prevention: 2007 Guideline for Isolation Control Precautions
- Centers for Disease Control and Prevention: Herpes Zoster
