Chickenpox
(Varicella · Chicken Pox)
In this condition factsheet:
The Facts on Chickenpox
Chickenpox is a preventable illness caused by the varicella-zoster virus. It was very common before the varicella (chicken pox) vaccine was introduced. It is extremely contagious, but the rash that it produces is usually harmless and disappears on its own.
While you can get chickenpox at any age, most cases occur before the age of 14. Anyone who's had the disease once is usually immune for life, although they can still get shingles, a painful skin rash caused when the varicella-zoster virus becomes active again, even many years after they've had chickenpox.
Chickenpox usually occurs during the school year; it is less common during the summer months. Since the introduction of the chickenpox vaccine, many children never get chickenpox.
Causes of Chickenpox
The varicella-zoster virus may be spread through the air when an infected person coughs or sneezes or by direct contact with the blisters (lesions) of someone infected with chickenpox or shingles.
The risk of getting chickenpox is higher for people who have had contact with an infected person, are under 12 years old, have a weakened immune system, or who work or spend time in a school or daycare facility.
Once someone is infected, the virus usually incubates for 14 to 16 days before a rash appears, although incubation can last from 10 days to 21 days. There are no symptoms during incubation and a person doesn't become contagious until 1 to 2 days before the rash appears. The person remains contagious until all the blisters have dried and scabs have formed.
To prevent the spread of the virus to others, people who have or are suspected to have chickenpox should avoid public places, such as school, until they feel well enough to perform their normal activities. Certain settings may have more specific policies regarding when to return following chickenpox infection.
Symptoms and Complications of Chickenpox
Flu-like symptoms start to develop a day or two before an itchy red rash appears. Fatigue, mild headache, fever, chills, runny nose, and muscle or joint aches are typical. The rash emerges as raised red bumps that turn to teardrop-shaped blisters that are extremely itchy.
These blisters may appear anywhere on the body, usually starting on the face, scalp, and torso, then spreading to the arms and legs. In some cases, the rash may even spread across your entire body, including areas such as the throat, mouth, anus, and vagina.
The blisters come in waves, with new crops developing as old ones burst. New blisters stop forming within about 5 days. By the sixth day, most blisters will have burst, dried, and crusted over. Within 21 days, most of the scabs will have disappeared.
Children usually have a much milder infection and recover faster than adults, infants, and adolescents. People with weakened immune systems also tend to have more severe and longer-lasting symptoms.
More severe and longer infection also comes with a higher risk of developing complications, including inflammation of the brain (encephalitis) and pneumonia.
Newborns of birthing parents who develop chickenpox during early pregnancy are at risk for low birth weight and birth defects. If the birthing parent develops chickenpox a week before birth to 2 days after birth, the newborn is at risk of a life-threatening infection.
Children who have had the chickenpox vaccine but did not develop full protection from the vaccine can still get chickenpox. However, they usually have a much milder case with a smaller number of blisters.
Cellulitis (a skin infection from bacteria) is by far the most common complication in children. It may leave scarring, especially if the child scratches the lesions. Necrotizing fasciitis ("flesh-eating disease") in children, though extremely rare, can occur as a complication of infection entering through the chickenpox lesions. Chickenpox blisters that appear in the mouth, throat, or anus are very uncomfortable. If the rash appears near the eyes, consult your doctor.
The varicella-zoster virus is never completely gone once it has entered your body. Anyone who's had chickenpox carries dormant viruses in the roots of their nerve cells. These can sometimes reappear years later as shingles, a painful skin rash that affects a particular area of skin.
Shingles can appear at times of emotional stress, or when the immune system is low. It's not always known what has provoked the virus to come out of hiding. It's important to know that the shingles rash can transmit chickenpox. People who have already had chickenpox or are vaccinated are immune, but people who haven't can get the virus from someone with shingles.
