The long arm

[dreamer_easy]

I found it -- the description of nanomachines being splashed onto a man, reproducing, and suddenly hitting critical mass: "The crete does nothing for a moment. It's in the long flat part of the exponential curve. Then, like a switch has been flipped, it sinks through his clothes, eating." It's in Daniel H. Wilson's short story "Small Things". The long flat part of the curve is what we lived with, with COVID-19 -- it was coming for such a long time, from so far away, and then BOOM! (See also comparisons with Lancelot's arrival at the wedding in Monty Python and the Holy Grail.)