Chickenpox, also called varicella, is a highly contagious illness caused by primary infection with varicella zoster virus (VZV).

It spreads easily through coughing or sneezing of ill individuals or through direct contact with secretions from the rash. A person with chickenpox is infectious 2 days before the rash appears, till vesicles are crusted (approx. 3-7 days after onset of rash). 

Symptoms start after 10-21 days of exposure. In children, the symptom is fever which is usually mild, but can reach upto 106F.  Also headache, malaise, anorexia, the development of a vesicular rash ie appears like boils. Lesions come in crops, which begins on the trunk and then spreads to the face and limbs. 

Varicella is a self resolving illness. Rarely, there can be complications like superinfection, pneumonia, encephalitis, bleeding, perinatal infection etc. Vaccinated cases usually have only mild rash with shorter duration, and little or no fever. 

Diagnosis of chickenpox is clinical, usually no tests required. Varicella treatment mainly consists of easing the symptoms like fever, itching on rash. Antiviral drugs are only given in special situations. 

Children affected with chickenpox need to be isolated at home to prevent spread to others.  Varicella can be prevented by vaccination- 2 doses are given at 12-15 months, and 4-5 years of age. 

People who develop chickenpox once have lifelong immunity to the illness, but can develop herpes zoster later in life.