Excellent article. This one is going into my file. Thank you @jeffkrol
Now, as this article discusses, columnaris, depending on the strain, can be either acute or chronic. Young fish are primarily the worst for wear under the acute strain that can kill fish within 12-48 hours- without external symptoms. This is probably the strain ( supposedly there are 4) that is most readily seen in fish that get at the LFS. Many of these fish are young, straight out of mass fish farms out of Florida.
Adult and aged fish would already be in an aquarium, often times, and the columnaris bacteria already present in system waiting for a way in through environmental stress: whether it be : through poor water quality, con-specific stress, nutritional deficiencies, etcc...
As this article states, in the aquarium, a more virulent strain of columnaris, in the absence of fish to infect, can turn into a less virulent strain to sustain itself- to save energy.
This may be why sometimes you will see a total wipe-out in n aquarium of fish that an aquarist got from the LFS. In between adding another group of fish, the more virulent strain alters itself to a less virulent, more chronic strain.
Later, in time, when or if a stressor occurs in the aquarium that lowers the immunity of the fish, this pathogen can can a foothold. But, to complicate it even more, the rate of transmission depends also on temperature, alkalinity/acidity, and redox potential.
So, I dont think of columnaris as a pathogen that requires a total breakdown of the aquarium and sterilization as you would a viral infection like tuberculosis. Sure, the most virulent strain that takes out a whole tank can make one pause-- consider a sterilization of tank--- but, even healthy fish have been shown to bring the most virulent strain in on their gills without being infected themselves. This demonstrates that, like so many other bacterial infections in the aquarium, a healthy fish ( maintained through healthy water quality, low stress among con-specifics, and high nutrition) is the best defense.