My First "Sick Day"

Hi everyone! Well, I am home sick today, having caught strep throat from my little friends. But I can't complain about my strep throat, because there is a little kid in my class who has it much worse!
Phoebe and Pewee are a brother and sister, ages 4 and 3, in the at-risk class. Phoebe was out sick all last week. Parents have to report cases of strep, and other highly contagious illnesses, to the school. So we found out that Phoebe had strep throat, and a note had to be sent home to all of the children letting them know that someone in their class had strep. 
At the beginning of this week, Pewee cheerfully reported that his sister was in the hospital... but the next day, Phoebe showed up at school! The poor little kid was as white as a ghost, with dark circles around her eyes, and she barely said a word all day. The day after that, Phoebe stayed home from school again. 
So yesterday, the kids' mom called to let Mrs. Wing know that Phoebe was in the hospital again. Apparently the strep throat spread to her heart, and Phoebe went into cardiac failure!!!
How does that happen? I had strep throat all the time when I was a little kid. I probably had it at least once each winter. (I was also plagued with frequent colds and ear infections... I was a very sickly little kid!) But I never went into cardiac failure! I've known many, many children who had strep throat, and nothing like this has ever happened to them. So how does a four-year-old child have a common childhood illness one minute, and be in the cardiac ICU the next? 
I had a mild sore throat, the day we found out Phoebe was in the hospital. I wondered vaguely if I might have strep. I don't have health insurance, being a student, so I wasn't even considering going to the doctor with a sore throat that mild.  But last night I was tossing and turning all night with my sore throat, and at some point in my somewhat delirious state, I decided I was going to stay home and go get a strep test. If it was strep, I didn't want to be the one to pass it on to another child, who might end up in cardiac failure! 
I went to immediate care, and sure enough, I have strep throat. So I guess its a good thing I stayed home... but I won't be able to find out until Monday about what happened with Phoebe! It is sort of driving me crazy. I really only knew Phoebe for four days... because she's only been to school for four of my eight student teaching days... but I keep picturing her pale face and sad eyes on that one day that she came back.
Everyone... if your little kids have sore throats, take them to the doctor right away! Maybe catching it sooner is a way to prevent this from happening to other children! I hope.