W32.Nimda.E@mm is a new version of W32.Nimda.A@mm
that contains bug fixes and other modifications, which are designed to prevent antivirus programs from detecting this variant.
For additional information, read the Microsoft TechNet article, "Information on the "Nimda" Worm
For information on .enc detections, read the article, "What is an .enc detection?
Click for a more detailed description of Rapid Release and Daily Certified virus definitions.