One of the biggest challenges with strep throat is trying to determine whether it is caused by the bacteria or if it is a viral infection that is causing the throat to be sore. Sore throats can also be caused by simple irritations. One of the ways to determine whether or not it is a virus or irritation that is causing a sore throat or if it is in fact strep throat is the duration of the symptoms. A person who has a viral infection or an irritation of the throat will typically only experience a sore throat for a short amount of time.
If strep is the cause of the sore throat the symptoms will tend to be more severe and will often last for a much longer period of time. If you have had a sore throat for more than a few days and your throat is red and irritated, chances are that it is strep throat.