Can a boy go steril before he hits puberty, if so can scarlet fever make u steril?

Technically a boy is sterile before he hits puberty since his body isn't making sperm. That's what sterility is. And yes, Scarlet fever, or any high temp fever will temporarily cause sterility since the sperm need a specific temp range in order to be produced properly. As to absolute sterility caused by Scarlet fever or a other diseases, it is a rare (very rare) side effect and is possible. but not probable. The only way to really tell is to test for mobility once the boy has been able to ejaculate for a number of months. The first month or two can be nothing more than seminal fluid and therefore contain no sperm at all. But given time, nearly all boys produce sperm. If you are concerned, a simple test can be done to determine whether or not your boys are swimming. Or buy a high powered microscope (not just the walmart brand) and see for yourself.

It is extremeley rare for a boy to be made sterile by scarlet fever. However tests have shown it can happen if the boy had very severe scarlet fever in his testicles, which is also rare. Hope this helps sorry I can't give you a more positive answer.
Unfortunately medical facts speak for themselves.