According to a press release from Panda Software, 7.2% of computers worldwide analysed by the company were infected with the Klez-I virus (as of April 27.) And that's only one variant, there are many more.
The sad part is that the virus exploits a flaw in Microsoft Outlook that was patched months ago. Also, the Panda Software release says many infected users had not kept their antivirus software up to date. Why haven't people updated? This seems like a simple concept to us.
Microsoft Outlook patch