Strep throat is a contagious bacterial infection that can be quite painful. The incubation period for strep throat can vary. It is typically about 3 days, although it can be anywhere from 2 to 5 days.
This means that from the time you are exposed to the illness to the time you start having symptoms will be about 3 days.
If you are sick with strep throat, you will be contagious until you have been on antibiotics for at least 24 hours. Note, however, that your symptoms may last longer than that.
If you have been infected with the bacteria and are not on antibiotics, you will be contagious for up to 3 weeks, even if you don't have symptoms.
It is very important to seek treatment for strep throat, as leaving it untreated can lead to very serious complications such as rheumatic fever.
"Strep Throat." National Institute of Allergy and Infectious Diseases 09 Mar 09. National Institutes of Health. 08 June 09.