What Causes A Shingles Outbreak?

Shingles, also called herpes zoster, is a painful condition that most often affects adults over 50. While in most cases, it is not a serious condition, it can be extremely unpleasant.

So, what causes shingles and how do you get it?

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What causes shingles?

Shingles are caused by varicella zoster, the same virus that causes chickenpox. Before routine vaccination, the majority of people caught chickenpox as children. Now, most children are vaccinated.¹

However, the chickenpox vaccine is a live attenuated vaccine, which means that vaccinated people are still at risk of developing shingles.

When somebody catches shingles (or is vaccinated with a live vaccine), the virus hides in reservoirs in the nerves. Once the virus is in your system, it typically stays there for the rest of your life. The vast majority of people can only catch chickenpox once, thankfully, but this viral reservoir can be activated, triggering an outbreak of shingles.

What are the symptoms of shingles?

The classic symptom of shingles is a rash on the body, on one side and not crossing the midline. Less commonly, the rash can be more widespread, but this is typically only in people with compromised immune systems. More rarely, the rash can affect another part of the body, including the face.

Typically, the area becomes painful, itchy, or tingly a few days before the rash shows up. It then develops into clusters of vesicles, which usually heal in two to four weeks, although they can leave scars. The rash can be painful enough to interfere with daily activities. 

Other possible symptoms are headache, photophobia, and/or malaise, which sometimes occur before the rash breaks out. In some cases, pain may last for an extended period after the rash clears up.

Understanding what triggers a shingles outbreak

Not everyone who has chickenpox will get shingles. Most people who get shingles only get it once unless they are immunocompromised.

You cannot "catch" shingles. However, if you have never had chickenpox, you can catch the virus through direct contact with a shingles rash. In this case, you will get chickenpox, not shingles.

People with shingles should keep their rash covered, especially if they are around somebody who is unsure whether they have had chickenpox and have not been vaccinated.

It is not known exactly why shingles outbreaks happen, but most cases are thought to be caused by lowered immunity. This means that the following are risk factors:

  • Old age. Most cases of shingles occur in people over 70, and it is rare in people under 40.

  • Stress

  • Conditions that affect your immune system, such as HIV

  • Being on medication that can suppress the immune system, such as corticosteroids

  • Recently having had a bone marrow or organ transplant

  • Chemotherapy.

Shingles can sometimes seem to appear out of the blue, and you may never know what triggered the outbreak. Being vaccinated against chickenpox can, since it's a live vaccine, result in shingles. However, the risk is lower than with natural infection.

Can children get shingles?

It's rare, but children can get shingles. Typically, pediatric shingles happen in children who were exposed to chickenpox very young. This includes in-utero exposure if the child's mother had chickenpox 5 to 21 days before giving birth.

These children have a small chance of developing shingles before the age of 5 because their immune system is not yet fully developed.

Older children exposed to chickenpox in kindergarten or younger can rarely get shingles a few years later or in adolescence, but this is unusual. The chickenpox vaccine has significantly reduced the incidence.

How are shingles diagnosed?

Shingles are typically diagnosed by examining the rash. The shingles rash is similar to that experienced during chickenpox but is typically more localized.

Testing for antibodies to the varicella virus is not typically done to diagnose shingles, as most people carry it, and those antibodies are found in people who have been vaccinated. But in most cases, the shingles rash is distinctive enough to provide a solid diagnosis.

How are shingles treated?

The vast majority of cases of shingles self-resolve in two to four weeks. There are two major treatments that are typically recommended:

  • Antivirals. The antivirals used are acyclovir, valacyclovir, and famciclovir. They can shorten the length and severity of the disease but need to be taken as soon as possible after the rash appears.

  • Pain medication. Your doctor may prescribe you a pain reliever or may recommend an over-the-counter pain reliever.

Home remedies to reduce itching can also help. These include calamine lotion, wet compresses, and colloidal oatmeal baths, which is a warm baths using ground-up oatmeal. There is no instant cure for shingles, but treatment can help improve your condition faster and make symptoms more bearable.

Is shingles an autoimmune disease?

No. Shingles are caused by the reactivation of dormant varicella zoster and are a complication of having had chickenpox. It is not related to any autoimmune disease.

Are shingles hereditary?

As yet, no genetic factors have been found that are related to your risk of getting shingles after having had chickenpox. However, it does appear that people with shingles are more likely to report that a family member had shingles. Thus, there does appear to be a genetic susceptibility and further research in this area is needed.

So, while shingles are not technically hereditary, genetics may explain why some people get shingles and others don't.

Are vaccines effective against shingles?

Being vaccinated against chickenpox lowers your risk of shingles. While the vaccine can cause shingles, it is at a much lower rate.

There is also an approved vaccine, Shingrix. This vaccine is delivered in two doses and is recommended at the age of 50 and to adults with weakened immune systems. It is also recommended that people vaccinated with the older vaccine, Zostavax, get Shingrix as it is substantially more effective.

In older adults, Shingrix is more than 90% effective. Shingrix is a reactogenic vaccine, meaning it tends to have more side effects than some other vaccines. However, the side effects are much less severe than getting shingles. Consider scheduling your vaccine for a time when you can take a day off work in case you get side effects.

The lowdown

Shingles are caused by a reactivation of varicella zoster, the same virus that causes chickenpox. Anyone who has had chickenpox is at risk of getting shingles, but it is more common in older adults and particularly common after the age of 70. There is also a small risk of shingles if you were vaccinated against chickenpox.

You cannot catch shingles from another person, but if you have shingles, you can potentially give the virus to somebody who has not had or been vaccinated against chickenpox. They will get chickenpox, not shingles.

The best way to keep from getting shingles is to get vaccinated as recommended by your doctor. Young children should be vaccinated against chickenpox, and adults 50 or older should receive the shingles vaccine.

  1. Shingles | National Institute on Aging

Other sources:

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