In Latin, "virus" is a mass noun, like "stuff", "water", or "poison", its original meaning. There is no attested plural. Being of originally Greek origin doesn't help matters.
In English, there's never a reason to use anything other than "viruses".
> Latin plural is viri
Actually, virus is a "mass noun" (uncountable) and has no plural. If it ever had a nominative plural it would be vira, and out of anything, viri is its genitive singular.
Re:The Deal That Makes No Sense
by dragonwriter on Tuesday September 03, 2013 @01:56PM
(#6322510)
> Word is from Latin - Latin plural is viri.
No, that's the Latin plural of vir; viri means "men" not "poisons" ("virus" means "poison" in Latin.) [1]
http://www.google.com/#q=translate+viri+from+latin+to+englis...
http://lysy2.archives.nd.edu/cgi-bin/WORDS.EXE?virus
In English the plural is viruses.