We have to become certified in something called GAP, what a PIA but if they find something in fresh produce it will be known exactly which field it was from and who picked it. It will prevent other farmers from losing their income because the problem will be able to be traced within hours.
There are places in the US that have this system now, and it should be expanded.
That said, anybody could have infected this shipment. I thought it was probably Moroccan labor (wiping with the left hand and all that yuck!) but it appears to be unidentified now.
The moral of the story is that we should all take precautions...or grow our own. Or not worry about it.
I’d hate to die from eating lettuce, but I guess there’s worse ways to go.