There's a possibility of your terrorist "plague" scenario, akenaton, but I believe it far more likely, that a "plague scenario" would arise spontaneously and be spread unwittingly by non-terrorists, witness the SARS epidemic.

Paranoia is a weird and dangerous thing, it skews your perspective regarding other more likely dangerous possibilities that result from being alive. But then, "paranoia" is useful in preventing populations of nation states from fully grasping what's really going on.

Carrying your reasoning farther, I suppose because most of the virulent flu viruses and such, tend to arise in southeast Asia and China, the West should get back in there too and do a bit of "premptive restructuring".

I'm sure that there are a lot of fundamentalist Buddists that live in very crowded conditions with their livestock and poultry, who eat very weird things and practice an odd form of medicine by our western standards, that need straigtening out too, in order for "us" to feel really safe.