Our son's situation sounds similar to yours. His first episode was at about 4 1/2 and it was caused by strep. After the initial episode he had future episodes with coxsackie (hand, foot, & mouth), mono, walking pneumonia etc...
His primary symptoms are always tics. We've only seen OCD once. Often when he gets a viral or bacterial infection the first way we know he is sick is because the tics start. When he gets strep he never gets a sore throat, but he has tics. Once the infection has passed the tics subside.
We are 3 years into this and he is on proph. Augmentin which works pretty well for him. For the most part he is symptom free about 9 months a year, then the winter comes and a virus wipes him out for a month or two..