>virus is by Latin definition a masculine noun<

Hi Ted,
Since the teaching of Latin is not so widespread anymore, it might not be superfluous to recall that in spite of its relative regularity, even Latin has its fair share of exceptions to formal rules. Those are probably mostly taught in the third and following years (-: ... But I have scanned the Web in the meantime, and "virus" seems to be a somewhat contentious case, not concerning its gender, which is recognized throughout as neuter, but with respect to its declension. There are no instances of its plural in the old literature.