In this case, the possibility of contracting AIDS is extremely low. Someone used this towel about two or three minutes ago. This person is not necessarily an AIDS patient. If not, he certainly won't be infected with AIDS. Assuming that this person is an AIDS patient (unlikely), there must be no blood on the towel. If there was blood, you wouldn't use it. If there is no blood, there is no skin damage. If there is no skin damage, there will be no exchange of body fluids. If there is no exchange of body fluids, it will not be infected.