i don't think that the question of whether the rapist is taking retroviral drugs should be of much consideration when determining the charges that are being laid. hiv is not a spectrum disease, and the risks of contracting it should not be weighed like you would play odds at a casino. any risk of transmission at all - no matter how negligent - should be considered equivalent, and come with equivalent sentencing.

http://www.cbc.ca/news/canada/saskatchewan/hiv-positive-status-to-factor-into-regina-rapist-s-sentence-but-not-criminal-charge-1.4216714