Yes, shingles is caused by a virus called varicella-zoster virus (VZV), the same virus responsible for chickenpox. VZV belongs to the herpesvirus family and is a DNA virus that infects only humans. After you recover from chickenpox, the virus doesn’t leave your body. It hides in nerve cells and can reactivate years or decades later as shingles.
How the Virus Stays in Your Body
When you first catch chickenpox, VZV travels through your bloodstream and eventually settles into clusters of nerve cells near your spine and skull called the dorsal root ganglia and trigeminal ganglia. There, it essentially shuts itself down. The virus’s genetic material forms a small loop of DNA inside the nerve cell’s nucleus, and the cell’s own chemistry keeps the virus silenced so it can’t reproduce. This dormant state is called latency, and it lasts for life.
Research shows the virus maintains itself in roughly 2 to 5 percent of sensory neurons, with a median of 5 to 7 copies of its genome tucked inside each infected nerve cell. You feel no symptoms during this phase. Your immune system keeps the virus in check, and for many people it never wakes up again.
What Makes the Virus Reactivate
Shingles occurs when the dormant virus “wakes up” and begins replicating again, traveling back down nerve fibers to the skin. The primary trigger is a weakened immune system. This can happen naturally with aging, as immune function gradually declines over time. It also happens with conditions or treatments that suppress immunity, such as organ transplants, certain cancers, HIV, or chemotherapy. About 30 percent of people will develop shingles at some point in their lifetime, with the risk climbing sharply after age 50.
Stress, illness, and physical trauma have also been linked to reactivation, though the exact tipping point varies from person to person. In some cases, there’s no obvious trigger at all.
Symptoms Before and During the Rash
Shingles typically announces itself before any rash appears. Several days beforehand, you may feel pain, burning, itching, or tingling in a specific area of skin. Some people also develop a fever, headache, sensitivity to bright light, or a general sense of feeling unwell. Because there’s no visible rash yet, this early phase is often mistaken for a muscle strain or other problem.
The rash itself follows a distinctive pattern. It appears in one or two bands (called dermatomes) that correspond to the path of the affected nerve. Most commonly, this means a stripe of blisters wrapping around one side of the torso, though it can also appear on the face. The rash almost never crosses the midline of the body. Clusters of small, fluid-filled blisters form over 3 to 5 days, then gradually dry out and scab over. The entire episode typically lasts 2 to 4 weeks.
How Shingles Spreads
You can’t catch shingles from someone else, but you can catch the underlying virus. If you’ve never had chickenpox or the chickenpox vaccine, direct contact with fluid from a shingles blister can transmit VZV to you. The result would be chickenpox, not shingles. Once the blisters have crusted over, the person is no longer contagious. Shingles does not spread through coughing or casual contact the way chickenpox does.
Treatment and the 72-Hour Window
Because shingles is a viral infection, antiviral medications are the primary treatment. These drugs work best when started within 72 hours of the rash appearing. Studies show no loss of effectiveness whether you start treatment at hour 12 or hour 70, so there’s no need to panic, but waiting beyond that window reduces the benefit significantly. Even after 72 hours, treatment may still be offered if symptoms are severe or complications are developing.
Antivirals shorten the duration of the rash, reduce the severity of pain during the active episode, and lower the risk of complications. Pain management is the other major piece of treatment, since shingles pain can range from mild to debilitating depending on which nerves are involved.
Postherpetic Neuralgia and Other Complications
The most common complication of shingles is postherpetic neuralgia, pain that persists for 90 days or more after the rash heals. In a study of nearly 120,000 shingles patients, about 5.8 percent developed this condition. The risk rises with age: an estimated 12.5 percent of shingles patients aged 50 and older go on to develop it. The pain can last months or even years and significantly affects quality of life, often described as burning, stabbing, or electric-shock sensations in the area where the rash appeared.
When shingles affects nerves near the eye, it can cause vision problems or, in rare cases, permanent eye damage. Shingles on the face can also affect hearing or cause facial muscle weakness if certain nerves are involved.
Vaccination Reduces Risk Dramatically
The recombinant zoster vaccine (sold as Shingrix) is the most effective way to prevent shingles. In clinical trials, it reduced shingles incidence by 97.2 percent in adults 50 and older and by 89.8 percent in those 70 and older. The CDC recommends the vaccine for all adults 50 and older, given as two doses separated by 2 to 6 months. Adults 19 and older with weakened immune systems are also recommended to get vaccinated, with the option of receiving the second dose as early as 1 to 2 months after the first.
You can get the vaccine even if you’ve already had shingles, since the virus remains in your nerve cells and can reactivate more than once. You can also get it if you don’t remember whether you had chickenpox. Most adults born before 1980 in the United States were exposed to VZV during childhood, so the virus is likely present even without a clear memory of the illness.