What the article says is that the virus contains a lot of specific code aimed at defeating anti-virus -- both the AV software itself, and the analysis techniques used by AV developers to figure out what the virus does. In the specific paragraph you quote, that's the latter which is discussed: the virus code alters its behaviour when it detects that it is running in an emulator.
Theoretically, a virus can always be defeated by a human being following the code "by hand". However, it is tiresome and takes quite some time. In practice, AV companies have nowhere near the time and resources to do manual analysis of every new brand of virus, which is why they need to rely on some semi-automatic techniques such as emulators. This is a losing battle in the long run...
Obligatory rant: a computer virus can exist and strive only because of flaws in the structure or implementation of computer systems -- in particular indulging in execution of code of dubious provenance. An example of a system which is well designed in that matter is a Linux distribution: executable files may come only as packages from official repositories, and the provenance is controlled with signatures. It is not "perfect" but the rarity of virus in the Linux ecosystem is suggestive that they do something right at some point. The best defence against virus is to fix the flaws. AV are like a new layer of paint to hide the crevices.