When you have a sore throat, you usually have two immediate questions: a) Is it strep throat? b) Am I contagious?
The first question has to be answered by a doctor's test (particularly if your sore throat lasts longer than 48 hours), while the second one is dependent on the answer to the first.
Short response: if you have strep throat, yes, you are most definitely contagious.
According to Dr. Jennifer Shu on CNN, you are most contagious a few days before symptoms show, and until approximately 24 hours after starting antibiotics to treat it.
Admittedly, this isn't the most useful advice in terms of prevention (how can you protect people if you don't even know you're sick?), but it does help determine whether or not your loved ones will get ill. If it's been at least five days since you started showing signs of strep, or more than a day since you started medication, people around you should be just fine.
For more information on strep throat, like symptoms and treatment, check out the slideshow below: