Don, an exponential spread of infection results in an epidemic.
Most do not. They may become endemic.
Think streptococcus, rabies, salmonella, etc.
AIDS has resulted in epidemics in some communities where transmission is high, but outside Africa that has not happened among heterosexuals. And it has had ample opportunity. It is no longer a new disease.
Don, there is no heterosexual epidemic here.
Never mind what Royston or I say. Look it up.
I have put up enough evidence now.
If you do not have anything new, please shut up and go away.