If you’re in your 40s, I have a great trick for getting people to spontaneously tell you how young you are: develop shingles. Friends, acquaintances and medical professionals will rapidly inform you that the painful rash is an older person’s disease and, “You’re a bit young to get that, aren’t you?”

I say this because at the tender age of 43, I have come down with a horrible case of ocular shingles. When I first went to urgent care about a weird red spot on my nose, a swollen eye and a terrible headache, the nurse looked dubious when he told me it might be shingles. “You’re a bit young,” he said. When I then went to the ER as instructed – shingles near the eye is a medical emergency that can blind you – the ophthalmologist said the same thing. According to conventional medical wisdom, shingles is a disease you get if you’re elderly or immunocompromised.

But that wisdom is outdated. Shingles is becoming significantly more prevalent among immunocompetent people under 50 globally, particularly women. Funnily enough, just a few days before I got sick,........

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