You mentioned having a "cold"...
Untreated strep throat can be a very bad deal. The infection can spread to your heart valves and vegetation can start to grow on them. The vegetation is actually the accumulation of bacteria.
This is why it is so important if you have any signs of strep throat you get on an antibiotic immediately, especially if you are febrile (with fever).
I work in the medical field and am telling you, I see cases related to untreated Strep infections way too often!
I was of the impression that the odds of this 1 in 50000....