I have no virus'

The plural of virus is viruses. Google it if you don't believe me, or read what Tom Christiansen wrote about it. What you have here is the possessive form. Unless you left off a word, and you meant to say you don't have [something that belongs to a virus], then your formulation is incorrect.

PS: I try to avoid being the grammar police around here, but some things I can't ignore. Improper use of apostrophes is one of them.