Tom, we *do* have a medical/biological advisor, whose primary
comment on the notion that a virus couldn't pass between one species
and another..."We have yet to contact one other alien life form to make
an analysis. We do not know for a fact that their biology will be
radically different than our own. Until we actually make contact, it's
as likely as not." A biologist works from what's known; unless you've got
a specimen of alien life somewhere and aren't showing it to anyone, or
you're simply making a guess, which is neither more nor less correct until
we have something testable in our hands.

jms