It should teach both IT and department managers that the music, smartphone and storage devices employees bring in are far more likely to be infected by malware than email that makes it through spam and AV filters inside the corporate firewall.
USB drives are hand carried by employees past the firewall, however, and plugged directly into computers with solid access rights the malware can use to infect not only that machine, but desktops and servers one, two or even three network hops away.
USB keys may be the best source of malware infections on your network. If you're having a lot of trouble with repeated infections, try making users scan USB drives before anything can come off them onto the network.
It won't solve your problem, but it may block a lot of the virii that show up on the network without IT or security knowing where they came from.
Oh, and stay off the commuter trains going in and out of Sydney. With that high a percentage of malware on the USB drives, there's no telling what else you might catch.