Viruses. In English, at least. In Latin, it would be vira. Third declination, not second.
And while I can at least understand that people who don't understand Latin but somehow learned that -us becomes -i in plural (yes, if it's 2nd and masculine instead of neuter), where the fuck does that second "i" come from?
Your answer is confusing, even though the result is correct.
Morphologically speaking, "vira" would be the proper plural precisely because "virus" is a second (not third) declension neuter noun.
Yet, it "virus" like "water" is uncountable so this plural is unattested.
But why do we always end up in this same Latin grammar and philology lesson?