Face-to-face exposure to someone with early chickenpox will put you at risk of infection. Even spending some time in the same room as a person with early chickenpox will put you at risk.
The highest risk is associated with living in the same household as a person with chickenpox. Nine out of 10 people who have not had chickenpox before will contract the disease under these circumstances.
Generally children are least likely to have complications from chickenpox. Babies under one year old are more vulnerable, and from puberty onwards teenagers and adults are more prone to severe chickenpox and its complications.
Certain groups of people are particularly at risk for severe chickenpox. Children and adults whose immune systems are compromised are at particular risk.
Examples of conditions that compromise the immune system include various forms of cancer, leukaemia, lymphoma and HIV/Aids.
Some drugs, such as high doses of cortisone used for severe asthma, arthritis or kidney diseases may compromise the immune system.
Immune-compromised people are prone to an extensive and severe rash, possible damage to internal organs, including pneumonia or hepatitis, to haemorrhagic chickenpox and to a prolonged course of the illness. Chickenpox may even be fatal in immune-compromised people.
Symptoms of chickenpox
Revised and reviewed by Prof Eugene Weinberg, Paediatrician and Paediatric Allergist, Health24 expert, February 2015.