The FDA announced on the 29th that all spinach implicated in the current outbreak has traced back to Natural Selection Foods LLC of San Juan Bautista, California. They have not yet identified the field or fields (if that's the ultimate origin) or whether the contamination arose from the handling of the spinach at the NSF processing plant. So far, it still looks to me like a small spot contamination spread nationally. The state of Washington has experienced E. Coli contamination of raw milk, the same O157:H7 strain that is particularly virulant. Is it industrialized processing methods? Or, are the little bugs evolving? It doesn't take much to get infected. The FDA reports: Infective dose -- Unknown, but from a compilation of outbreak data, including the organism's ability to be passed person-to-person in the day-care setting and nursing homes, the dose may be similar to that of Shigella spp. (as few as 10 organisms).
Here's a 1997 map depicting the 157:H7 isolates by state showing it appears in many places.
I've often been struck by the disproportion between the death statistics and the measures we adopt to deal with particular causes of death. It has seemed to me, for example, that the reaction to 9-11 and terrorism in general is extraordinarily out of proportion with its statistical significance -- and that massive over-reation contributes to making terrorism effective as a political strategy...
I think E. coli is evolving. Back when I was a bacteriology student, we used E. coli a lot for doing experiments in trait transference and genetic modification. Why? Because the little bugger is a genetic sponge. It will pick up traits from lots and lots of other bacteria it comes in contact with, and happily incorporate them into itself. The fact we were so casually experimenting with it in this manner, despite destroying the cultures in autoclaves and flaming everything else, still worries me.