Is the Merchant real?

In both versions of RE4, the merchant only shows up after Leon’s been injected with Las Plagas. I always wondered why?

Could it be that the merchant is a figment of Leon’s imagination as he’s slowly but surely succumbing to the infection?

In the original, Paul Mercier voiced both Leon and the Merchant which supports the argument that Leon is essentially hallucinating and talking to himself throughout the whole game. Any thoughts?