The risk is so incredibly low, given the information you have given.
Especially when we are dealing with a child in good health.  After all,
a child gets HIV from his mother usually, during pregnancy, so that they
are in poor health from the very first days or weeks of life.  Indeed,
they often die by a year or two of life.  If the child is in good health
I don't think there is a measurable risk of continuing breastfeeding.

Jack Newman, MD, FRCPC