How long is someone contagious for when they have the common cold, flu, or bacterial / viral bronchitis?

Contagious periods: The contagious period differs for each type of infection, even among different viruses! there is a range of values based on different infections ranging from common cold to influenza. These vary from 24 hours to up to 2 weeks! you should ask your physician what infection you have and for how long you will be contagious. Common sense dictates that respiratory viruses travel by cough or sneeze.