Varicella-zoster virus (VZV) is one virus, but it causes two very different diseases. That's why it has a hyphenated name. VZV causes varicella, or chicken pox, in children and adults who didn't have chicken pox as kids. The same virus causes herpes zoster, or shingles, in adults who had chicken pox as children.
All children with chicken pox have VZV in their blood. The virus can also make its way to internal organs. And it nearly always finds its way into nerves during a bout of chicken pox.
Although virtually all children recover fully from chicken pox, they do not kill off VZV; instead, the virus lurks in their nerves in an inactive form for as long as they live.
Uncanny Ability to Survive
VZV survives in nerve cells in regions called dorsal root ganglia. Most people have no clue that their nerve cells are harboring VZV; indeed, the virus is harmless in its dormant form. But if it comes to life and begins to reproduce, VZV can damage nerves, which causes pain. The virus also travels down the nerves to the skin, causing a rash that's confined to the regions where the nerve endings are distributed. The combination of a localized rash and pain may sound familiar to you: it's the shingles.
Shingles is familiar because it's so common. Since the chickenpox vaccine was not introduced until 1995, over 95% of Americans over age 25 have had childhood chickenpox. And nearly all harbor VZV in nerve cells. In most, the virus remains inactive, but over the course of a lifetime it will kick up in about 30% of people, causing shingles. In all, about 1 million people come down with shingles in the United States each year.
Shingles can occur at any age, but it's most common over age 60. People with impaired immune systems are at highest risk, but most people with shingles are in good health until the disease appears out of the blue, without evident cause.
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Pain is usually the first symptom. It's usually a mild to moderate burning or tingling sensation, but it can be a severe knife-like or deep boring pain. Two to five days later, a rash appears. It is difficult to diagnose shingles before the rash breaks out, and many patients are treated for other conditions during this time. In fact, more than a few healthy gallbladders have been removed because of severe pain in the right side of the abdomen, only to have the rash appear after surgery.
Like the pain, the rash is confined to the area of the body that's near the inflamed nerve. It forms a band that occurs on just one side of the body, most often on the chest or abdomen. ("Zoster" comes from the Greek word for "belt" and "shingles" from the Latin word for "belt".)
Shingles can affect the face. This is less common but more worrisome, because the eye can be involved. An ophthalmologist should treat any eye inflammation.
The shingles rash looks like a miniature version of chicken pox: a tiny fluid-filled blister surrounded by a red rim, the "dew drop on a rose petal." The rash can be unsightly and uncomfortable. It crusts over and heals in 7-14 days, sometimes leaving small scars behind. The pain, unfortunately, is another story. It can last for weeks, months, or even years. This so-called post-herpetic neuralgia (PHN) may be mild, but it can be excruciating. Older people have a higher risk for persistent pain; about 40% of patients over 60 develop PHN. Other complications are much less common.
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Doctors can diagnose most cases of shingles simply by looking at the rash. But if necessary, the doctor can collect a drop of fluid from a blister and test for the virus.
In the past, doctors couldn't do much to treat shingles. They prescribed pain killers, antihistamines for itching, and compresses soaked with Burrow's solution to keep the rash clean and prevent secondary bacterial infections. These measures are still important, but additional treatments can now reduce the risk of persistent pain.
Doctors can now prescribe a drug that will actually stop VZV in its tracks, preventing the virus from replicating itself. The U.S.Food and Drug Administration (FDA) has approved three medications for shingles that are equally safe and effective:
- Acyclovir (Zovirax) - 800 milligram dose taken 5 times a day
- Famciclovir (Famvir) - 500 milligram dose taken 3 times a day
- Vvalacyclovir (Valtrex) - 1,000 milligram dose taken 3 times a day
Each medication should be taken for 7 days. Side effects are uncommon but may include nausea, diarrhea or headaches.
To be effective, these antiviral medicines must be started as early as possible, ideally within 3 days after the rash appears. But many doctors give the medicine to patients with severe shingles even after the 3-day window. And patients with major complications should receive acyclovir ntravenously.
A 1996 study found that combining antiviral drugs with a steroid drug, such as prednisone, may lead to faster healing and a lower risk of post-herpetic neuralgia. Subsequent trials have been much less encouraging, but some doctors still recommend adding a brief course of prednisone to antiviral therapy for older patients with herpes who don't have diabetes, glaucoma or other conditions that might be worsened by steroids.
Taking an antiviral drug is a big advance in treatment, but it's not perfect. It will never kill off dormant VZV in the nerve ganglia. So patients can still develop second (or third) attacks of shingles. That makes prevention the best treatment (see Prevention below).
Treating the Nerve Pain
It may be very difficult to treat pain that lingers in the wake of shingles. Ibuprofen is ineffective, and aspirin and acetaminophen are only marginally helpful. Even prescription painkillers often fail.
The FDA has approved a skin cream, capsaicin (Zostrix, Qutenza) for PHN. It causes a burning sensation and then reduces pain. It doesn't always help. Capsaicin should never be used early in shingles, when the rash is still present.
Perhaps the most effective medicines are the tricyclic antidepressants, such as amitriptyline (Elavil). They reduce or eliminate pain in about half the people who've tried them for PHN. Side effects may include dry mouth, constipation, sleepiness and low blood pressure. Men with enlarged prostates can develop urinary retention and elderly people can become confused.
If the tricyclics fail, doctors may turn to anticonvulsants, such as gabapentin (Neurontin, generic) and pregabalin (Lycra). Neurologists and pain specialists may help with nerve blocks and other treatments. Nontraditional approaches such as relaxation, biofeedback, and other cognitive and behavioral therapies may also help reduce pain.
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Is it Contagious?
Adults cannot catch shingles from children with chicken pox. But children (or adults) who have never had chicken pox or the varicella vaccine can get chicken pox after coming into close contact with the shingles. If you have shingles, keep your distance from infants, children and pregnant women who are not immunized, as well as people with impaired immune systems.
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How To Prevent Shingles
Many of us remember when nearly every kid got chicken pox. Those days are gone, thanks to the varicella vaccine (Varivax), which was approved in 1995.
The vaccine contains a live but greatly weakened version of VZV. Two doses are recommended for all children with normal immune systems. The first dose should be given between 12 and 15 months of age; the second dose should be given between 4 and 6 years of age. Older children and adults who never had the vaccine or chicken pox itself should also get two doses (given 4 to 8 weeks apart) unless they were born before 1980, are pregnant or have impaired immune systems. The vaccine is safe and it has nearly eliminated chicken pox in the United States. Only time will tell if it will also live up to the promise of reducing the risk of shingles in future generations.
Most adults grew up before the chicken pox vaccine was available, but that doesn't mean they have to take their chances with shingles. In 2006, a vaccine against shingles (Zostavax) was approved for adults age 60 and older. In 2011, the approval was extended to people 50 and older.
The shingles vaccine contains the same weakened VZV strain as the chicken pox vaccine, but in a much higher dose. The vaccine cuts the incidence of shingles by more than 50%, and it reduces the risk of post-herpetic neuralgia by more than 66%. The most common side effect is pain at the injection site, which is usually mild.
The shingles vaccine should not be given to people whose immune systems have been weakened by certain cancers, therapy with steroids or other immune-suppressing medications, or HIV infection. Although the vaccine trials did not include people who had an earlier bout of shingles, it seems likely that they will benefit from the vaccine, as second attacks of shingles are common without this protection. Doctors don't yet know how long the vaccine's protection will last or if booster shots will be needed.
Keep an eye out for future developments. Keep the other one on your skin for now. If you spot a rash that might be shingles, see your doctor promptly. If you start an antiviral drug in time, it can help speed healing and reduce your risk of persistent pain.
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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.
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