Spoiler alert: you are super contagious. From one or two days before the spots even appear until all the blisters have dried into scabs (usually about 5–7 days), you are basically a walking biohazard.
If you were around a pregnant woman, a newborn, or someone with a weak immune system, you’d better call them and apologize. The virus travels through the air when you cough or sneeze, and it can even live on surfaces for a few hours. Yes, even that doorknob you touched an hour ago.
Chickenpox - NHS
