Varicella zoster (chickenpox and shingles)

In the third of our series on systemic disorders and the eye, Dr Iain Phillips looks at a very common infection, chickenpox, its ocular effects and related infective conditions

Chickenpox is a viral illness caused by the Varicella zoster virus of the Herpes family. Chickenpox is a disease unique to humans, meaning the only reservoir is a human population. The disease is spread from person to person through the respiratory system. Chickenpox is primarily a disease of children. Over 90 per cent of cases in developed countries occur in those under 13 years of age.¹

The disease incubates for approximately two weeks before the characteristic rash appears. Patients are infectious and able to give the disease to others over a period of time ranging from two days before the rash appears until the rash lesions are crusted over (five days after the rash appears). The appearance of the rash is associated with the dissemination of the virus in the bloodstream, after the virus has infected the respiratory epithelium. In Western Europe adult cases of chickenpox are rare. This disease is, however, more common in adulthood in the developing world.

Chickenpox is one of the two forms of clinical disease caused by the Varicella zoster virus. The second is shingles, this is the reactivation of the virus after primary infection. Shingles can develop many years after the primary infection. After primary infection the virus becomes latent (inactive) and hides in the dorsal root ganglia.²

Shingles is a common disease. It particularly occurs in the elderly or those who are immunosuppressed. The risk of shingles increases as the ability of the body to raise a cell-mediated immune response decreases.³