Box 22 Herpes Zoster – The Same Virus, a Different Disease

In 10–20% of children infected with varicella, the virus takes up residence in nerve cells, where it lies dormant for several decades, until a lowering of the host’s immune defences (as a result of ageing, disease, or immunosuppressive treatment) allows it to awaken, begin replicating, and precipitate herpes zoster disease, or shingles as it is commonly known . In the United States alone, 43 million people are believed to be at risk of herpes zoster. 

Herpes zoster is characterized by a painful blistering rash along the distribution of the infected nerve cells. In many elderly people the rash and pain subside and resolve completely in a few weeks. In about 15% of patients, though, pain and numbness in the area of the rash can last for weeks or months. The pain can be severe and highly disabling, both physically and mentally. Itching, which may fluctuate from mild to intense, adds to the person’s discomfort. In addition, 8–15% of people suffer permanent neurological damage, impaired vision, or problems of bowel or bladder function. Elderly people and immune-compromised people run the highest risk of developing herpes zoster. Since the same virus causes varicella, people with herpes zoster constitute a source of varicella outbreaks among unvaccinated children and other non-immune population groups. 

Treatment with antiviral drugs is effective if started soon after the onset of herpes zoster. However, accurate diagnosis at that stage of the infection is difficult and in most cases antiviral treatment is begun too late to be of optimal benefit . In 2005, a vaccine against herpes zoster was licensed for use in people over 60 years of age. 

It contains at least 14 times the amount of virus as the varicella vaccine. Its protective efficacy, though, varies with the recipient’s age, falling from 64% in the 60–69 year age group to 41% in the 70–79 year age group, and 18% in the 80–89 year age group. Some herpes zoster experts believe younger age groups – such as people in their 50s, who account for almost 20% of herpes zoster cases – could benefit from the vaccine. 

Two factors, though, militate against its widespread adoption by developing countries: price (the vaccine currently costs about US$ 150 a dose in industrialized countries), and the low public health priority of herpes zoster in relation to the many other serious diseases that ravage these countries.

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