Why does chicken pox cause shingles later on in life?


Why does chicken pox cause shingles later on in life?

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>Shingles and chickenpox are distinct human diseases but are closely related in their life cycles. Both originate from infection of an individual with the varicella zoster virus (VZV). Chickenpox, also called varicella, results from the initial infection with the virus, typically occurring during childhood or adolescence. Once the chickenpox has resolved, the virus can remain inactive (dormant) in human nerve cells (dorsal root ganglia or cranial nerves) for years or decades, after which it may reactivate. Shingles results when the dormant varicella virus is reactivated. Then the virus travels along nerve bodies to nerve endings in the skin, producing blisters. During an outbreak of shingles, exposure to the varicella virus found in shingles blisters can cause chickenpox in someone who has not yet had chickenpox; this initial infection will not trigger shingles, however. How the virus remains dormant in the body or subsequently re-activates is not well understood.


99% of adults have had chickenpox at some stage of their life. After infection when you’re a kid, the virus lies dormant in your nerve cells for the rest of your life. It can randomly reactivate in adulthood when an nerve cell or a few nerve cells gets triggered by stress, another infection or immune system being under attack, sometimes theres no cause.

The awakened virus fizzes out that nerve cell onto the surface of the skin usually causing the classic shingles symptoms – blisters, pain and itching. These occur where the nerve cell is located. More nerve cells are attached to the spine than anywhere else which is why the classic grape-like red rash occurs on the torso most often. Shingles can occur anywhere though, depends where the nerve cell in question is, if its in the eye it can get really serious.

Shingles is not contagious. The only thing you can catch from someone suffering from shingles is the chickenpox (and only if you’ve never had the chickenpox) – and you’d need to be touching the shingles blisters directly to catch it

It’s sort of like in a horror movie – the baddie always comes back one more time.

The virus which causes chickenpox lies dormant but sometimes reactivates in adult life. Nobody really knows what triggers it, but being re-exposed to the chickenpox virus (EG. If your kids get it) is NOT how it happens.

It’s the same virus. You get chickenpox first at some point (usually childhood or adolescence). The virus is quite widespread and you get the typical rash (you can be asymptomatic or only have one or two spots so don’t realise you’ve had it. I had this as I had my blood checked before I started medical school to see if I should get vaccinated before seeing immunocompromised patients, but blood work shows I’ve had the virus before). You then recover from the chickenpox

The virus however remains in your body in one or more dorsal root of spinal nerves or cranial nerves. Here it is relatively protected from the immune system. Later on in life something triggers re-emergence of the virus and you get chickenpox again, but only in the area that that nerve innervates. And this is shingles.

You need to have had chickenpox earlier to get shingles and something is needed to happen to trigger shingles developing. These things are more likely to occur as we age so they happen later. Shingles in childhood is uncommon/rare. The trigger may not be identified but mostly are things that reduce the immune response (eg immunosuppressive drugs or disease, psychological stress, aging)