Shingles is chickenpox coming back after decades in hiding

**Shingles (herpes zoster) is caused by the reactivation of varicella-zoster
virus — the same virus that causes chickenpox.**

The sequence is:

1. Primary infection with VZV causes varicella (chickenpox).
2. Afterwards, the virus remains dormant in the dorsal root ganglia — the
   nerve roots beside the spine.
3. It can reactivate later in life as herpes zoster, a painful
   maculopapular and then vesicular rash.

The virus never left. It has been sitting in a nerve root, sometimes for sixty
years.

Who is a candidate

Anyone infected with varicella can develop herpes zoster — and **about
99.5% of people born before 1980 in the United States have had wild-type
VZV.**

Essentially everyone of a certain age is carrying it.

**Children who receive the varicella vaccine have a lower risk of herpes
zoster than children infected with wild-type VZV.** Which is a long-term
dividend of chickenpox vaccination that was not its original purpose: a
generation with less latent virus to reactivate.

Prevention and risk

Shingles can be prevented with the Shingrix vaccine.

**Older adults and people who are immunocompromised are at high risk of
complications** — which is the group the vaccine is aimed at, and the group
for whom shingles is not merely unpleasant.

The diagnostic difficulty

**Herpes zoster is hard to diagnose in children and younger adults,
especially if the clinical presentation is mild.**

The classic picture — a painful band of blisters along one dermatome in an
older adult — is easy. A mild rash in a twenty-year-old is not, and shingles
is not usually the first thing considered at that age.

Source: Centers for Disease Control and Prevention.