According to Symantec, the OSX.Flashback.K infection is declining each day. The current number of infected Macs is now around 140,000, down from 600,000 a week ago.
If you think you may be infected, you can run a Flashback removal tool from either Kapersky or F-Secure. Apple also has a tool for Lion users without Java installed. OS X users should install the latest Java update from Apple which will protect you from a future infection.