What Causes Shingles (Herpes Zoster)?

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Published: 25 April 2021

What is Shingles?

Shingles (also known as herpes zoster) is a viral infection caused by a reactivation of the varicella-zoster virus (VZV) that causes chickenpox (varicella) (Better Health Channel 2020).

When someone first becomes infected with VZV, they will contract chickenpox. However, after chickenpox resolves, the virus will stay dormant in the dorsal root ganglia (nerve cells in the spine) and may reactivate later on in life (CDC 2020).

For this reason, only people who have had chickenpox are at risk of shingles (Healthdirect 2020).

Shingles presents as a painful, blistering rash. The reactivated virus generally affects one or two adjacent dermatomes, which are areas of skin that are mostly supplied by a single nerve root branching out from the spinal cord (Oakley 2015; Wiggins & Seervai 2020; DoH 2020).

Each of these nerve roots runs from one side of the spine to the anterior middle of the body and sends pain sensations from the dermatome they supply to the brain. For this reason, the rash caused by shingles forms a stripe or belt-like pattern on one side of the face or body (chest, back, abdomen or pelvis) without crossing the midline (Montana.gov 2013; DoH 2020; Healthdirect 2020).

How Does Shingles Spread?

Shingles can only occur after chickenpox - it is not possible to catch shingles from somebody else who has shingles (Murrell & Roth 2018). However, the varicella-zoster virus itself is contagious and can be transmitted through contact with fluid from the blisters caused by shingles (DoH 2020).

If a person with shingles transmits VZV to a person who is not immune to the virus, the nonimmune person will develop chickenpox. A person who has previously had chickenpox can not catch VZV from another person as they already have it in their body (Murrell & Roth 2018).

shingles herpes zoster effect on others diagram
(Adapted from Murrell and Roth 2018)

Shingles is much less contagious than chickenpox (VIC DoH 2015).

Risk Factors for Shingles

Anyone who has had chickenpox may develop shingles, but it is most common in people over 40 (Healthdirect 2020). It can occur in children, but this is not as likely (VIC DoH 2015).

It is estimated that one-third of people who are not immune to chickenpox or shingles will develop shingles during their lifetime (Healthdirect 2020).

There is often no identified trigger for the reactivation of the varicella-zoster virus (Healthdirect 2020). However, known risk factors include:

  • Being over the age of 60
  • Physical or emotional stress
  • Living with human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS)
  • Having an organ transplant
  • Having a recent bone marrow transplant
  • Undergoing treatments for conditions such as cancer that affect the immune system.

(Healthdirect 2020)

Shingles usually only occurs once per lifetime, but some people (especially those who have a weaker immune system) may experience it more than once (Healthdirect 2020).

Shingles Symptoms

The first symptoms of shingles may include:

  • Pain in the affected area
  • Burning, tingling or itching in the affected area
  • Stabbing sensation in the affected area
  • Sensitivity to touch in the affected area
  • Numbness in the affected area
  • Photophobia (light sensitivity)
  • Fever
  • Headache
  • Fatigue
  • Enlarged, tender lymph nodes near the affected area.

(Healthdirect 2020)

The characteristic rash will generally appear a few days after the onset of these initial symptoms, affecting the area of skin where the discomfort (i.e. burning, tingling or itching) is occurring. It usually persists for 10 to 15 days. During this period, small lesions will erupt and form blisters that fill with liquid, burst and then crust over (DoH 2020; Oakley 2015). This can cause scarring in some cases (Better Health Channel 2020).

shingles herpes zoster rash

Recovery usually takes two to three weeks in children and young adults, and three to four weeks in older adults (Oakley 2015).

Older adults and those with weakened immune systems are at higher risk of more serious symptoms (DoH 2020).

Complications of Shingles

Shingles usually resolves without issue. However, some people may experience complications such as:

  • Post-herpetic neuralgia (pain that persists for more than three months after the shingles rash has resolved)
  • Temporary or permanent vision loss caused by shingles in the eye area
  • Bacterial infection of the rash
  • Pneumonia
  • Hearing issues
  • Meningoencephalitis (swelling of the brain)
  • Hepatitis
  • Palsy in the cranial or peripheral nerves
  • Death.

(Healthdirect 2020; DoH 2020; CDC 2020)

Seek medical advice if a patient with shingles is experiencing:

  • Confusion
  • Memory loss
  • Severe headache
  • Eye-related symptoms
  • Fever over 38°C.

(Healthdirect 2020)

Treatment of Shingles

Shingles is not curable, but antiviral medicines can be used to alleviate symptoms and reduce the risk of complications (Healthdirect 2020). Antivirals are most effective if started within three days of rash onset (Better Health Channel 2020).

Other management strategies include:

  • Taking over-the-counter paracetamols and non-steroidal anti-inflammatories for pain relief
  • Ensuring the rash is kept dry and clean
  • Avoiding scratching, as this may aggravate the rash and lead to infection or scarring
  • Gently patting the rash dry with a clean towel after showering or bathing
  • Wearing loose, cotton clothes in the affected area
  • Using cool compresses, cool baths or ice packs to alleviate discomfort (ice packs should not be placed directly onto the skin)
  • Avoiding using creams or gels on open blisters (as this increases the risk of infection).

(Healthdirect 2020; DoH 2020; CDC 2020)

How is Shingles Prevented?

shingles herpes zoster zostavax vaccination
Zostavax is recommended for all Australians over the age of 60 and given for free to all people aged between 70 and 79.

The risk of developing shingles can be reduced through a vaccination known as Zostavax, which is recommended for all Australians over the age of 60 and given for free to all people aged between 70 and 79. While Zostavax is not a guaranteed protection against shingles, it reduces the likelihood that it will occur (Healthdirect 2020).

Zostavax contains 14-times more live varicella-zoster virus than the chickenpox vaccine and therefore should not be given to immunocompromised people (Better Health Channel 2020).

The chickenpox vaccine, which is generally received during childhood, is effective in preventing chickenpox in the first place in 70 to 90% of people (VIC DoH 2015).

People who have shingles should take preventative measures to avoid spreading the varicella-zoster virus to those who are not immune (i.e. those who have not had chickenpox or the chickenpox vaccine). They should:

  • Cover the rash (if possible) with a non-stick dressing
  • Refrain from touching or scratching the rash
  • Perform frequent hand hygiene
  • Refrain from sharing towels, playing contact sports or swimming
  • Avoid contact with:
    • Pregnant women who have not had chickenpox or the chickenpox vaccine
    • Premature or low birth weight neonates
    • Children who have not had chickenpox or the chickenpox vaccine
    • Immunocompromised people (e.g. people undergoing chemotherapy, people taking immunosuppressants, people who have had a transplant, people living with HIV).

(DoH 2020; Healthdirect 2020)

The shingles rash is no longer contagious once it has crusted over (DoH 2020).

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