If there was ever any doubt (and there wasn’t), it is gone now:  The cucumber plant at the east end of the row is infected with bacterial wilt.  I yanked it out and tossed it on the refuse pile (which is far enough from the garden to prevent spread of the disease).  I also made sure that the garden snippers—another possible source of cross-contamination—were clean (having a chlorinated pool next to the garden comes in handy sometimes).

So far, there are no signs of it spreading to the other cucumbers (but I will keep my eyes on them).