JPEG virus; true or false

I’m confused. In 2002 there was an announcement that a virus called Perrun was the first virus to infect .jpeg files. Computerworld published an article discussing whether or not this program posed a real threat. This is not a new phenomenon. Way back in 1994 there was a hoax warning on the net about a similar kind of thing. Today there’s another story about a ‘new’ .jpeg virus threat. Is this all just hype? Anyway, I can’t find any suggestion that Macintosh computers are at risk so maybe I should welcome more bad press for Windows.