you won't ever get a virus from the site, posts, or PM's just by opening up the message. JUST DON'T EVER CLICK ON A LINK IN A POST OR PM IF YOU DON'T KNOW WHO IT'S FROM OR IF IT LOOKS SUSPICIOUS!
Clicking on an outside link, that leads away from this site, is where you will catch the virus, if there is one! Most of these spammers are just promoting their own websites, no threat of virus'. It just more of an annoyance than anything else!