Chickenpox is a common viral childhood infection usually affecting school age children.

It is caused by the varicella zoster virus (part of the herpes family). This disease is marked by a characteristic rash - usually starting on the head and moving downwards, small red bumps appear which later become blisters which in turn later become crusted. Associated symptoms include fever, decreased appetite, reduced activity and feeling sick.

Chickenpox is highly contagious, the virus being spread primarily through aerosolized particles in coughs and sneezes. The incubation period for chickenpox is usually between 1 and 2 weeks long, so symptoms may appear unexpectedly, making tracing exposure difficult. The infected child is infective from a few days before the first rashes appear to until all the rashes are crusted over. This may take 2 to 3 weeks. Most children suffering from chickenpox have to be kept home away from school for a period of time.

Recently, a vaccine for chickenpox has become available.