Causes of shingles

Shingles is caused by the reactivation of the varicella-zoster virus, which is the virus that causes chickenpox (a highly infectious condition that most people have during childhood).

After you have had chickenpox, the varicella-zoster virus lies dormant (inactive) inside your body. It can later be reactivated and cause shingles.

It is not known exactly how the virus is reactivated, but it may be linked to having lowered immunity (protection against infection and diseases).

Your immunity to illness and infection can become lowered if there is a problem with your immune system (the body’s natural defence system). This can happen as a result of:

  • Being older. As you age, your immunity may decrease. Shingles most commonly occurs in people over 80 years old.
  • Physical and emotional stress. The chemicals released by your body when you are stressed can prevent your immune system from working properly.
  • Having HIV and AIDS. People with HIV may be up to 25 times more likely to get shingles than the rest of the population.
  • Recently having a bone marrow transplant (bone marrow is the spongy material in the centre of some bones). The conditioning you receive before the transplant will weaken your immune system.
  • Recently having an organ transplant. You may need to take medication to suppress your immune system so your body accepts the donated organ. After a transplant, 25-45% of people may develop shingles.

It is not possible to catch shingles from someone else with the condition. However, it is possible for someone who has never had chickenpox to catch chickenpox from someone with shingles. In the UK, chickenpox is so common during childhood that 9 out of 10 adults have had it, so will not be affected.

Catching chickenpox

The blisters (vesicles) that develop as a result of shingles contain virus particles. The virus can be spread through direct contact with the open blisters. If you have not had chickenpox before, you can catch it from direct contact with:

  • the fluid from the blisters of someone who has shingles
  • something that has the fluid on it, such as bed sheets or a towel.

If you have shingles, you are contagious until the last blister has scabbed over. This will usually occur five to seven days after your symptoms started.

Spreading the virus

If you have the shingles rash, do not:

  • share towels or flannels
  • go swimming
  • play contact sports.

This will help prevent the virus being passed on to someone who has not had chickenpox.

People to avoid 

If you have shingles, avoid:

  • women who are pregnant and have not had chickenpox before, as they could catch chickenpox from you, which may harm their unborn baby
  • people who have a weak immune system, such as someone with HIV or AIDS
  • babies less than one month old, unless it is your own baby, in which case your baby should have antibodies (proteins that fight infection) to protect them from the virus.

Once your blisters have dried and scabbed over, you are no longer contagious and will not need to avoid anyone.

Last updated: 04 September 2013

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