The problem I have is that the disease would have been almost certainly identified as (a) being artificial and (b) of American origin.
The USSR and China would launch their nukes...
The US would return the favor...
And that would be that.
(Remember, this was back when strategic warhead totals were in the 10,000+ range on each side.)
I agree 100%. It was a major plot hole that I saw immediately (When i read it I was part of a SAC wing, so my thinking was already in that direction) but then, if he'd done that part realistically, the book would have been reeeeeal short.
I picked up a phrase, BTW, from some post-apocalyptic science fiction novel, either Emergence or War Day. After describing a limited Soviet first strike (in War Day they only launched at 3 cities), the narrator describes the American response: "We broke every window in the Soviet Union."