Are there cases where strep throat cause immune system to attack heart but it is very mild to be considered rheumatic fever?
Doubtful. If you have confirmed strep throat, the treatment of amoxicillin or azithromycin would protect from rheumatic fever, scarlet fever, etc. There are other conditions that can cause systemic symptoms of fever and shortness of breath (Lemierre's syndrome). If the process was a viral syndrome e.g mononucleosis (which can cause an exudative tonsillitis) the fatigue, sweats would persist. See a doctor.
For people with rheumatic fever, after strep bacteria has stopped infecting, how long will immune system continue attacking the heart?
May be long term. Need to know the extent of involvement . Read more...
Before strep throat reaches level of rheumatic fever, do immune system already mildly attack body tissues?
Clarification. First, not all will develop rheumatic fever if untreated.The frequency is estimated at 1/200 untreated cases & what makes some do it and others not is unknown. Second, for those that will have 10 days to start treatment during which you can stop auto-antibodies to human tissue from forming. They would form antibodies to strep, just not auto-antibodies. Read more...