Option 1: Try to evolve some Code of Ethics which was self-evidently free from infection, and which when followed self-evidently tended to reduce and isolate the infected areas. This would provide a standard that the uninfected populace could rally to; the infected populace would either have to fake the Code and be identified, or defy the Code and reveal themselves. What this Code would be depends on specifics of the invading meme. I'm not sure I'm smart enough to come up with such a Code, but in that mess I'd try.
Option 1.1: A general extension of this principle is to pick battlegrounds where the infected side is obvious.
Option 2: If tech is advanced enough, turn the entire situation over to open-sourced AIs with a simple set of behavioral instructions.
Option 3: Require leaders to submit to a continuous realtime fMRI scan. It might not be able to tell the difference between a normal person lying and a infectee lying, but it should probably be able to tell the difference between a normal person reciting the truth and an infectee avoiding it, or between a normal deciding something emotionally and an infectee experiencing a massive Quarantine-like surge of loyalty. (If this doesn't work, it doesn't.)
Option 4: Take a small core group, mutually tested, and do your level
best to take over the minds of the entire government leadership,
infected or not. (Risky!) Once you have dictatorial powers, fix
everything, then put the leaders' minds back the way they were and
commit suicide to outrun the outraged populace.
--
sentience@pobox.com Eliezer S. Yudkowsky
http://pobox.com/~sentience/tmol-faq/meaningoflife.html
Running on BeOS Typing in Dvorak Programming with Patterns
Voting for Libertarians Heading for Singularity There Is A Better Way