> Under normal conditions, highly virulent strains of the virus are not selected. A highly virulent strain would kill the host before the virus would have an opportunity to transmit to other potential hosts and replicate. Thus, less virulent strains are selected.
This is not correct. What is selected against is deadliness, which is not correctly referred to as "virulence."
By example, the virulence of the kind of herpes that most Americans call "cold sores" is off the charts: you can get it from a single kiss. But because the host barely notices, it's not a big deal.
Similarly, a great number of diseases occur to AIDS patients because they're omnipresent, but cause no harm in normal conditions.
Don't even get me started on mononucleosis.
And then, of course, this is just a generalization; measles and many kinds of meningitis are ridiculously virulent, as well as extremely deadly.