When you have chickenpox as a child, the virus never actually leaves the body. Once you recover, the virus settles into the roots of your nerves and lays dormant. When the virus reactivates later in life, you get shingles. Only people who develop chickenpox, or get the chickenpox vaccine, will get shingles. But having chickenpox does not guarantee that you will have shingles later in life. Right now, no one is really sure what makes the virus reactivate. But scientists suspect there is a connection to a weakened immune system.
When the herpes zoster (or varicella-zoster) virus is reactivated in your nervous system, it begins to reproduce. Antibodies left over from chickenpox are supposed to neutralize it, but if your immune system is weakened, the antibodies won't be strong enough to stop the infection. As the virus multiplies in the sensory nerve clusters that alert your brain to pain and temperature, it spreads down your nerves to your skin and causes the painful rash.
During their lifetime, about 25 percent of adults will develop shingles, usually after age 40. As you get older, your immune system declines, which increases your chances of developing shingles. More than half of shingles cases develop in people over the age of 60. Scientists also speculate that exposure to children with chickenpox boosts immunity and prevents virus reactivation, and some older people may lack that exposure.
Some prescription medication can weaken your immune system, making you more vulnerable to infections like shingles. Some medications that weaken your immune system are:
An operation, such as an organ transplant, can also weaken your immune system.
Shingles is often seen in people who are suffering from certain medical conditions. Disease weakens their immune system, making them more susceptible to infection. Some of these diseases are:
If you have shingles, or think you do, you may want to see your doctor. Your doctor can make sure that shingles isn't a symptom of a larger problem. About 5 percent of people with shingles are found to have cancer, which is about twice the amount of people in the general public with undiagnosed cancer.
Babies are susceptible to many infections because their immune systems are immature. If a mother gets chickenpox at the very end of her pregnancy, the child may be born with chickenpox or develop it within a few days. These babies are more likely to develop shingles as children. About one third of children exposed to chickenpox in the womb, 5-21 days before birth, will develop shingles by age 5. We don't know why shingles reactivate in some people but not in others. But when you have a weakened immune system, you are more likely to be susceptible to the infection. The elderly, newborns, patients with certain diseases and those taking specific medications are all more likely to develop shingles.