Childhood Diseases

Updated 09 April 2018

What is chicken pox?

Chicken pox is very infectious and occurs worldwide as a childhood disease that lasts for 5 to 7 days.


Alternative name: Varicella

Chicken pox starts with a fever and a widespread rash of small blisters (vesicles), which are usually distributed on the chest, back, face, and the arms and legs. Sometimes the disease can be more severe, affecting internal organs (especially the lungs and liver).

Almost all of us will have only one episode of chicken pox in our lifetime, if at all. Once you’ve recovered, you’ll have life-long immunity to chicken pox.

The virus that causes chicken pox (varicella-zoster virus or VZV) belongs to the herpes virus family. It usually takes about 14 days from the time you’re exposed to the chicken pox virus to the time when symptoms start to occur. Sometimes this period can be as short as 10 days, or as long as 21 days.

The preliminary symptoms of fever and headache usually begin 24 to 36 hours before the rash appears. The fever subsides a few days after the rash appears, and the rash usually lasts for 5 or 6 days. It then starts to scab, dry and fall off. The last dried-up scabs fall off by 10 days.

Like other members of the herpes virus family, the chicken pox virus never really leaves the host after recovery from the initial infection. Instead, it remains hidden in certain nerve cells, without causing any obvious illness. This hidden or “latent” virus may be reactivated later by a variety of causes such as stress, malnutrition, or advanced age.

The reactivated virus will cause an illness called shingles (herpes zoster). Shingles is a band of painful blisters, usually involving the skin on the side of the chest or abdomen. It may involve the face.

Course and prognosis of chicken pox

Chicken pox is usually a mild illness in children, and most healthy children have a self-limiting infection that clears up after about 7 to 10 days. 

There are, however, a number of possible complications. But fortunately these are quite rare.
Chicken pox encephalitis may occur in about 1 in 1,000 cases, usually towards the end of the disease. If diagnosed early, treatment is available.

Chicken pox pneumonia is another possible complication, but is less common in children than in adults. Chicken pox pneumonia may be a very serious complication of chicken pox and may be fatal if not treated early, especially in adults.

Fortunately, anti-viral treatment is now available to treat it.

Reviewed by paediatrician Prof Eugene Weinberg. MBChB; FCP (SA); PAED (SA). March 2018.