What you need to know about shingles infections

• The lifetime risk of developing shingles is 30%.
• It is estimated that 99.5% of the U.S. population over age 40 is at risk for shingles.

It might begin with an inexplicable pain on one side of the body, on the face or the neck. Or you might have a rash on your midsection, arm or face that looks a little like poison ivy, but it hurts and itches.

If the pain and rash are on one side of the body, those symptoms might be caused by shingles, also known as the herpes zoster virus, which hides out in the nerve root endings after a chicken pox infection or vaccination, and can reappear at any time.

"It's estimated that 99.5% of the U.S. population over 40 is at risk because they've either had vaccine or the wild-type of chicken pox," said Dr. Allison Weinmann, senior staff in the division of infectious diseases for the Henry Ford Health System.

"Overall, people have about a 30% lifetime risk of getting shingles."

Although it most commonly strikes people older than 50, the incidence of shingles has steadily risen since the 1940s among people of all ages — and no one is quite sure why, said Dr. Rafael Harpaz, medical epidemiologist in the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention.

"We're talking about almost a fourfold increase," said Harpaz of data that show shingles struck almost 7.6 out of every 10,000 people in 1945-1947. Six decades later, 29.5 out of every 10,000 got the disease.

"I've given this as much thought as anybody, and I just don't have a good explanation for it," Harpaz said.

Anyone, no matter the age, who has had chicken pox or the vaccine for chicken pox can develop shingles, though Weinmann said it often is triggered in people with weakened immune systems and those older than age 50.

"Young people are not immune. It's a reactivation disease that can reactivate with trauma or surgery to the affected area; that can be a risk factor. It's not unheard of without any underlying disease or recognized drug affecting the immune system. But it is more common as you age."

Dr. Sanford Vieder, medical director of the Trauma Center at Beaumont-Farmington Hills, and medical director of Lakes Urgent Care in West Bloomfield, said when shingles does appear in younger, otherwise healthy people, it often leads doctors to ask additional questions.

"There is a mental checklist we go through and say, 'Hey, is there something underlying with this? Or is it just a random thing?' Maybe you were stressed out, or maybe you had a really bad viral infection recently and that was what sort of triggered things. Or do you have something underlying? That is something that should be evaluated if you do contract shingles."

He knows from personal experience that stress can be a factor.

"I had a very mild case of shingles when I was in my late 20s," Vieder said. "It was a particularly stressful time — I was just graduating medical school and was just starting residency, and I think that had a little bit to do with it. I was fortunate. I had a very mild case and it only affected my hip and my leg. But generally, especially cases where they affect the face, it can be devastating."

A complication called post-herpetic neuralgia can occur in some people with shingles. It causes intense pain that lasts longer than the rash, and can interfere with sleep and appetite. To reduce the risk of developing post-herpetic neuralgia, Vieder said it's important to get treated by a doctor as soon as symptoms appear.

"The earlier we start antiviral treatment … the shorter the duration and the lower the intensity of the breakout. It's really critical to get it started preferably within 72 hours of when symptoms begin."

There's no way to ward off a shingles infection, except to get the vaccine for it as soon as you're eligible, which is after age 50.

"It's important to get immunized, and we encourage people to do it," Weinmann said, noting that because it's a live and attenuated vaccine, some people aren't eligible for it. Those with immunodeficiency, pregnant women and those with advanced HIV disease aren't candidates.

For those who are, "it's been shown to cut both the risk of shingles altogether by about half and it decreases the risk of post-herpetic neuralgia by about 67%," Weinmann said.

"With this disease, almost everybody is at risk for it. The important thing to know really, is that there is not a lot you can do. There's a group of viruses like this that kind of hide out and can reactivate. But this one can be very debilitating and cause complications."

Contact Kristen Jordan Shamus: 313-222-5997 or kshamus@freepress.com. Follow her on Twitter @kristenshamus.