Varicella-zoster virus is the virus that causes shingles and chickenpox. Chickenpox is almost universal with 95% infection rate by age 21. However in other parts of the world, childhood chickenpox is less common leaving immigrants from developing countries susceptible to infection in adulthood with potentially serious consequences.
This virus, like the other eight human herpes viruses, remains latent in the body and may reactivate in response to ill-health, stress or trauma to the area. Shingles is the name given to these recurrences and is more likely to affect older people (50% at 85 years). Post herpetic neuralgia (PHN) follows shingles in a rising proportion of older patients: from 50% of 60 year olds with shingles to 70% of those aged 75.
Causes and Symptoms
Chickenpox (herpes varicella) is very infectious. It is self-limiting and rarely serious in children. Adults may, however, become seriously ill. After an incubation period of 14-21 days a febrile illness will develop followed by typical spots over most of the body. These may develop into ulcers before scabbing over and healing.
After the primary infection, herpes viruses remain latent in the body and may reactivate at a later date.
Varicella-zoster virus is called shingles if it recurs and the vesicles (spots) are localised, usually on head or chest. Shingles (herpes zoster) cannot be caught although it may be passed to susceptible persons as chickenpox.
In shingles, the vesicles and typical pain follow the line of the nerve. Neurological damage can leave symptoms, described variously as excruciating pain, scalded skin, deep aches, tingling, intolerable itching or shooting nerve pains. This post herpetic neuralgia may last months or years.
If the primary infection of chickenpox is severe, and when a shingles occurs in an older patient, one of three antiviral tablets may be prescribed: aciclovir, Famvir or Valtrex. Otherwise all that is necessary is to alleviate symptoms: antipyretics, analgesics, topical anaesthetics as appropriate.
Eye infection: Varicella-zoster virus may affect the ophthalmic division of the trigeminal nerve causing pain in, usually, one eye. Diagnosis is by fluoroscein stain. Treatment with antiviral ophthalmic cream as well as antiviral pills is recommended. Eye infection may damage sight or even, rarely, lead to blindness.
Because postherpetic neuralgia (PHN) becomes more prevalent with age, over 50s should be started on prescribed treatments to block PHN: a low-dose tricyclic anti-depressant.
If PHN develops gabapentin may be added to the drug regimen. Capsaicin cream has been successfully used in several trials.
Self-help such as firm bandaging or use of a TENS (transcutaneous electrical nerve stimulation) unit may alleviate the pain.
Reported PHN should not be dismissed by doctors as the constant sensations ranging from constant itching to acute pain may render the patient's final years an unendurable misery. Suicides have been recorded.
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