The WMD already here could be kilos and kilos of anthrax in glass jar "bombs" to fill thousands of envelopes, to to be thrown down on subway tracks, or into air intakes for buildings and sports arenas.
If they are dispersed to a dozen agents with no contact with each other, I can't see a solution.
I wouldn't say solutions are unimaginable. For anthrax, an effective and reasonably safe vaccine could well be enough. Speaking of the anthrax vaccine, haven't the Russians offered to sell or give theirs to us? Why haven't we taken them up on the offer -- is there some reason to think their vaccine is ineffective or excessively prone to side-effects?