Shingles and Chickenpox (Varicella-Zoster Virus)
Risk Factors for Chickenpox (Varicella)
Between 75 - 90% of chickenpox cases occur in children under 10 years of age. Before the introduction of the chickenpox (varicella) vaccine, about 4 million cases of chickenpox were reported in the U.S. each year. Since a varicella vaccine became available in the U.S. in 1995, the incidence of disease and hospitalizations due to chickenpox has declined by nearly 90%.
Chickenpox usually occurs in late winter and early spring months. It can also be transmitted from direct contact with the open blisters associated with either chickenpox or shingles. (Clothing, bedding, and other such objects do not usually spread the disease.)
A patient with chickenpox can transmit the disease from about 2 days before the appearance of the spots until the end of the blister stage. This period lasts about 5 - 7 days. Once dry scabs form, the disease is unlikely to spread.
Most schools allow children with chickenpox back 10 days after onset. Some require children to stay home until the skin has completely cleared, although this is not necessary to prevent transmission.
Recurrence of Chickenpox. Recurrence of chickenpox is possible, but uncommon. One episode of chickenpox usually means lifelong immunity against a second attack. However, people who have had mild infections may be at greater risk for a breakthrough, and more severe, infection later on particularly if the outbreak occurs in adulthood.
Risk Factors for Shingles (Herpes Zoster)
Shingles affects about one out of every three adults. About 1 million cases of shingles occur each year in the U.S. Anyone who has had chickenpox has risk for shingles later in life. Certain factors increase the risk for such outbreaks.
The Aging Process. The risk for herpes zoster increases as people age. The risk for postherpetic neuralgia (PHN) is also highest in older people and increases dramatically after age 50. PHN is persistent nerve pain and is the most feared complication of shingles.
Immunosuppression. People whose immune systems are damaged from diseases such as AIDS or childhood cancer have a risk for herpes zoster that is much higher than those with healthy immune systems. Herpes zoster in people who are HIV-positive may be a sign of full-blown AIDS. Certain drugs used for treating HIV, such as protease inhibitors, may also increase the risk for herpes zoster.
Cancer. Cancer places people at risk for herpes zoster. At highest risk for developing shingles are those with Hodgkin's disease followed by patients with lymphomas. Chemotherapy itself increases the risk for herpes zoster.
Immunosuppressant Drugs. Patients who take certain drugs that suppress the immune system are at risk for shingles (as well as other infections). They include:
- Azathioprine (Imuran)
- Chlorambucil (Leukeran)
- Cyclophosphamide (Cytoxan)
- Cyclosporine (Sandimmune, Neoral)
- Cladribine (Leustatin)
- Infliximab (Remicade)
- Adalimumab (Humira)
- Prednisone and other corticosteroids
These drugs are used for patients who have undergone organ transplantation and are also used for treating autoimmune diseases. Such disorders include rheumatoid arthritis, systemic lupus erythematosus, diabetes, multiple sclerosis, Crohn's disease, and ulcerative colitis.
Risk Factors for Shingles in Children. Although most common in adults, shingles occasionally develops in children. Children with immune deficiencies are at highest risk. Children with no immune problems but who had chickenpox before they were 1 year old also have a higher risk for shingles.
Risk for Recurrence of Shingles. Shingles can recur, but the risk is low (about 6%). Evidence suggests that a first zoster episode may boost the immune system to ward off another attack. However, people who had long-lasting shingles pain after their first episode, or patients who are immunocompromised, may be at higher risk for recurrence.