Chickenpox is a very contagious disease caused by the varicella-zoster virus. The virus spreads easily from people with chickenpox to others who have never had the disease or received the chickenpox vaccine. The virus spreads in the air when an infected person coughs or sneezes. It can also be spread by touching or breathing in the virus particles that come from chickenpox blisters.
Chickenpox can also be spread from people with shingles. Varicella-zoster virus also causes shingles. A person with shingles can spread the virus to others who have never had chickenpox or received the chickenpox vaccine. In these cases, the exposed person might develop chickenpox. For more information about how shingles spreads, see Transmission.
When Is a Person Contagious ?
A person with chickenpox can spread the disease from 1 to 2 days before they get the rash until all their chickenpox blisters have formed scabs.
It takes from 10 to 21 days after exposure to a person with chickenpox or shingles for someone to develop chickenpox.
If a person vaccinated for chickenpox gets the disease, they can still spread it to others.
For most people, getting chickenpox once provides immunity for life. However, for a few people, they can get chickenpox more than once, although this is not common.