Shingles comes from the same virus that causes chickenpox. If you had chickenpox at any point in your life, the virus never actually left your body. It went dormant in your nervous system, and shingles is what happens when that virus wakes back up, sometimes decades later.
The Virus Behind Shingles
The varicella-zoster virus (VZV) is responsible for both chickenpox and shingles. During a childhood chickenpox infection, the virus spreads throughout the body, causing the familiar itchy rash. Once the immune system fights off the active infection, though, the virus doesn’t get fully eliminated. Instead, it retreats into nerve clusters near the spine called ganglia, where it essentially goes to sleep.
The virus reaches these nerve clusters in one of two ways. It can travel backward along nerve fibers from the skin, riding the same pathways that carry sensation from your body to your spinal cord. Or it can hitch a ride on immune cells that migrate directly to the ganglia. Either way, once there, the virus settles into nerve cell bodies and goes quiet. Each infected nerve cell holds only a few copies of the viral DNA, and the virus produces almost no detectable proteins during this dormant phase. It’s hiding in a form your immune system largely can’t see.
This dormant state can last for years or decades with no symptoms at all. The virus is technically still alive inside your neurons, maintaining its genetic material at very low levels, but it’s not replicating or causing damage.
What Makes the Virus Reactivate
The immune system keeps the dormant virus in check through a type of ongoing surveillance. When that surveillance weakens, the virus can begin replicating again. This is why shingles risk climbs steadily with age: the immune system naturally becomes less effective at monitoring and suppressing dormant infections over time.
Beyond aging, several factors can tip the balance in the virus’s favor. A weakened or suppressed immune system is one of the biggest risk factors. About 30% of people hospitalized for shingles have a compromised immune system. Physical or emotional stress, major illness, certain medications that dampen immune function, and even surgery can create an opening for reactivation. Lab research has shown that disrupting specific cellular signaling pathways in neurons can restart viral replication, which helps explain why the body’s overall state of health matters so much.
Not everyone who carries the dormant virus will develop shingles, but the odds are significant. Your risk increases with every decade past age 50.
Why Shingles Appears in a Stripe
One of the most distinctive things about shingles is its pattern. The rash almost always shows up as a band or stripe on one side of the body. This isn’t random. It reflects the anatomy of the nerve where the virus was hiding.
Each spinal nerve supplies sensation to a specific strip of skin called a dermatome. These dermatomes wrap from the spine around one side of the body to the midline of the chest or abdomen. When the virus reactivates in a particular nerve ganglion, it travels down that nerve fiber and causes inflammation and blistering only in the skin territory that nerve serves. That’s why the rash rarely crosses the midline of the body. It’s confined to the territory of a single nerve root.
The most common locations are the torso and face, but shingles can appear anywhere a nerve supplies skin, including the eyes, scalp, and limbs.
Can You Catch Shingles From Someone?
You can’t catch shingles directly from another person. Shingles only develops from a virus already living inside your own body. However, the fluid inside shingles blisters does contain active virus. If someone who has never had chickenpox or the chickenpox vaccine comes into direct contact with that blister fluid, they could develop chickenpox (not shingles). Once the blisters crust over, the person is no longer contagious.
This means shingles poses a risk primarily to newborns, unvaccinated children, pregnant people who haven’t had chickenpox, and anyone with a severely weakened immune system who hasn’t been exposed to the virus before.
Nerve Pain That Outlasts the Rash
The rash itself typically heals within two to four weeks, but the virus can leave lasting damage. During reactivation, the virus inflames and injures the nerve fibers it travels along. In some people, this damage disrupts the way nerves send signals to the brain. Instead of transmitting sensation normally, the damaged fibers send amplified, scrambled pain signals.
This condition, called postherpetic neuralgia, can cause burning, stabbing, or aching pain in the area where the rash appeared. It can persist for months or even years after the skin has healed. The risk increases with age, and it’s one of the main reasons prevention matters.
Vaccination and Prevention
The CDC recommends two doses of the recombinant shingles vaccine for adults 50 and older, spaced two to six months apart. For adults 19 and older with weakened immune systems, the same two-dose series is recommended, with the option to shorten the interval between doses to one to two months when there’s a benefit to completing the series quickly.
This vaccine works differently from the older live vaccine (which is no longer available in the United States). The older version lost effectiveness rapidly, dropping to just 18% efficacy in people 80 and older within a few years. The current recombinant vaccine maintains substantially stronger protection across age groups, which is why it replaced the earlier option.
Even if you don’t remember having chickenpox, you may still carry the virus. Over 99% of Americans born before 1980 have been infected with varicella-zoster virus, and many of those infections were mild enough to go unnoticed or were mistaken for something else. Vaccination is recommended regardless of whether you recall a childhood chickenpox episode.