It sounds like something from a sci-fi movie: a virus that lingers in your body, lurking within your nervous system until it one day emerges without warning, often as a cluster of nasty blisters and a world of pain.
The risk of developing shingles grows with age, and just about every American is vulnerable. Nearly a third of us will develop it in our lifetime. While there's no guaranteed way to prevent the disease, its severity can be lessened by prompt treatment. And the shingles vaccine, approved for those age 60 and older, can lower your chances of getting it.
Shingles is caused by the varicella zoster virus, which is in the herpes family of viruses. It first appears as chickenpox and, like genital herpes, it never goes away.
Once someone has had chickenpox - or even the chickenpox vaccine, which contains the live virus - the virus sleeps in the roots of some nerves, often for decades, before awakening and reappearing as shingles.
According to the Centers for Disease Control and Prevention, shingles each year affects about a million Americans.
The shingles rate is gradually increasing. While the CDC says it doesn't know the reason, some experts have theories. Marc Siegel, an infectious-disease specialist at George Washington University Hospital, says a decline in the number of chickenpox cases may be making shingles more common. The CDC, however, says that the increase began before the United States began vaccinating children.
Shingles often strikes when people are in their 50s, but about half of the cases occur among those 60 and older, a group that's also more likely to endure a shingles complication called post-herpetic neuralgia (PHN). Affecting a third of those who get shingles after age 59, it results in pain or numbness that can last for months and sometimes years. That's why doctors recommend that people get a shingles vaccine once they turn 60 years old.
The most common early symptoms of shingles are itching, tingling or pain, followed by an angry red rash along the nerve path traveled by the virus - often across the torso, sometimes along the arm or leg. It may feel like a sunburn, or worse.
But not everyone displays those symptoms. Susan Elliott, a dermatologist in Washington, D.C., says, "About half the time, my patients have no itching or pain; they have a sudden appearance of bumps or blisters that appear on one half of the body."
The rash sometimes emerges on the forehead or tip of the nose, which is alarming because it can then involve the eye; if it does progress to the eye, it can cause vision loss.
The pain can be excruciating, some sufferers say.
Melissa Fossberg, 49, who lives in Washington and works for an international development organization, says that in 2010 she first felt a bit of irritation around her waist. That turned into "the worst pain I've ever had - a deep nerve pain. It felt like being stabbed with long, slender knife blades." She missed at least two weeks of work while recovering. "It was not fun," she says.
The rash and pain can be less severe if treated early, preferably within the first 48 to 72 hours after symptoms appear. The drugs used include acyclovir, famciclovir and valacyclovir.
Even though it's far more likely to strike later in life, shingles also takes plenty of younger people by surprise. Jen Middleton, 40, a mother of two who lives in Washington, was in her first trimester of pregnancy six years ago when she discovered a cluster of pus-filled blisters on the right side of her back. Middleton says that when her doctor told her she had shingles, "I said, 'What? Old people get shingles!' I had no idea." Her doctor pointed out that a woman's immune system slows during pregnancy, making her more vulnerable to the virus.
Some people cite stress as a cause of their shingles outbreak. Fossberg, for one, believes there's no coincidence that her shingles emerged while she was immersed in a difficult project at work. (According to the Centers for Disease Control and Prevention, though, there is insufficient research to establish a link with stress.)
"I think it's a myth," Siegel says. "Maybe if you're stressed it can cause the immune system to be less robust. We definitely do see episodes of shingles at times of illness. But often there's no apparent reason why the virus reactivates."
Note, too, that you aren't going to "catch" shingles; exposure to someone with active shingles is only a danger if you have never had chickenpox or the chickenpox vaccine, or if your immune system is seriously compromised, Olney, Md., dermatologist Paula Bourelly says.
"The risk in that case is developing chickenpox (not shingles), which can be life-threatening in adults," Bourelly said in an e-mail. And that can occur only from contact with the fluid in shingles blisters.
Zostavax, a weakened but live form of the chickenpox virus, is licensed by the Food and Drug Administration to reduce the risk of shingles in people age 50 and older.
But CDC's Advisory Committee on Immunization Practices recommends it only for those 60 and older, a guideline followed by most doctors. A clinical trial found that for people 60 and older, the vaccine cut their risk of developing shingles by about half and, maybe most important, their risk of PHN by 67 percent.
Adriana Lopez, a CDC epidemiologist, says that while the agency doesn't have a recommendation for routine use among those in their 50s, that age group "can talk with their health-care provider about whether or not to get the vaccine." (Some insurers don't cover the vaccine for those younger than 60.)
Even if you are sure you haven't had chickenpox, CDC recommends the vaccination if you're in the 60-and-older group. The vast majority of Americans born before the chickenpox vaccine was approved in 1995 have been exposed to the chickenpox virus, though some may not recall having symptoms as children.
And the CDC advises vaccination even for those who have had shingles, to decrease the chance of recurrence.
Despite all the recommendations, most Americans have been ignoring or are unaware of the guidelines: A 2012 CDC survey found that only 20 percent of adults 60 and older had been vaccinated against shingles.
Jim Greenfield, a music teacher in Washington, is 58. He recently found himself with "pain that went around my whole midsection." His brother, a doctor, diagnosed it immediately, even before a rash developed, and Greenfield was able to start medication quickly enough to put an end to the symptoms within a week or two.
"But it was pretty painful," he says. "Looking back, I should certainly have gotten the vaccine."