、。
Stupidity's contagious. Stay away.
Literal
Idiot [subject-が] transfers, approach[negative imperative-な].
A rough, contemptuous warning delivered in two curt clauses. 近づくな is the negative bare imperative form ('don't X!') — the most direct form of prohibition, blunt and confrontational. Usually used by men in rough or commanding contexts (warning signs, drill sergeants, angry parents). Pairing it with the colloquial idiom バカがうつる ('stupidity's contagious') — written in katakana here for extra bite — turns the whole utterance into a dismissive keep-away.