Herpes Zoster (Shingles)

Varicella zoster virus (VZV) is a herpesvirus, which can cause two major diseases: varicella (chickenpox) and zoster (shingles).

Varicella is a common childhood infection in Hong Kong. During primary varicella infection, VZV enters the cutaneous sensory nerve endings and migrates to the dorsal nerve root ganglia where it becomes latent. Reactivation of the virus in the form of zoster can occur at all ages, but is more common after 50 years of age or in people with a weak immune system.

Clinical manifestation of zoster

Typical zoster presents as painful skin rash with blisters distributed along a single stripe or section on either side of your body that is innervated by a nerve known as ‘dermatome’. Tingling or burning pain may precede the rash by 48 to 72 h. Zoster in patients with a weak immune system can be unusually severe, involving more than one dermatome.

The blisters usually dry up and crust over after 7 to 10 days. Some patients may have prolonged pain after the blisters have cleared. This is called postherpetic neuralgia, which may last for weeks or even months.

Zoster involving the ophthalmic branch of the trigeminal nerve (herpes zoster ophthalmicus) may result in inflammation of the cornea (keratitis) and uvea (uveitis). VZV can also cause acute retinal necrosis, which can lead to vision loss and warrants aggressive antiviral treatment.

Clinical management of zoster

Acute management of zoster lesions includes pain management, local treatment and specific antivirals.

1. Antivirals

In general, antivirals should be started within 72 hours of rash onset. Antivirals for VZV reduce viral shedding and duration of disease. They may also reduce the risk of postherpetic neuralgia. Acyclovir, valacyclovir and famciclovir are the first line medications. Treatment is continued for 7-10 days or until lesions have crusted.

Recommended standard doses of antivirals against zoster are as follows:

Indication	Acyclovir	Valacyclovir	Famciclovir
Localised zoster	800mg – 5 times/day (oral)	1g – 3 times/day (oral)	500mg – 3 times/day (oral)

Patients with kidney impairment need to take a lower dose of antivirals.
Disseminated zoster requires intravenous antiviral treatment.

2. Transmission

Direct contact with the fluid from blisters can spread VZV to others who have never had chickenpox or never received the chickenpox vaccine.

Ways to prevent spreading VZV to other people

1. Cover the rash if it is distributed in exposed areas e.g. face, limbs.
2. Avoid scratching the rash, try to keep blisters intact.
3. Wash hands often.
4. Avoid contact with the following people
     - Pregnant women
     - Infants
     - People with a weak immune system
e.g. people receiving chemotherapy, organ transplant recipients

Prevention

Vaccination can reduce the chance of getting zoster and the occurrence of its complications once it occurs, such as postherpetic neuralgia. Zoster vaccine is available in Hong Kong. You can ask your doctor for more details.

References

Centers for Disease control and prevention.
https://www.cdc.gov/shingles/index.html
National Health Service of United Kingdom.
https://www.nhs.uk/conditions/shingles/

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