There's never been an OSX virus AFAIK. And OSX has been around since 1999. Regardless of apple computer, if it runs osx it's safe. Prior to osx there were some much older mac viruses. Although I came across those mentioned from fellow students, I've never encountered one on the internet in any form or fashion. Windows viruses are well ... a plague. And for windows users of course we all have to be diligent. I scan my files regardless, even though 99.99+% of the virus definitions are for windows.