> There is no -ii ending in latin. At all.

Should you mean no -ii ending to "virus" at all, it would appear to be a reasonable assertion. However if by "at all", you mean of any word in Latin, that is demonstrably false.

http://latindictionary.wikidot.com/noun:filius

Nominative and vocative plural: filii

Usage example:

"... et nihilo minus amicum gravem virum aut fidelem libertum lateri filii sui adiungere, ..."

https://thelatinlibrary.com/quintilian/quintilian.institutio...