The only known one. The bacteria originated in an alien species called the Vajra, who were also at the center of a conflict that used music about a decade before the Var outbreaks around the Brisingr Globular Cluster, but spread out after the Vajra departed for another dimension.

[Which is a whole other can of worms to explain. At least the story of the Macross Frontier is recent enough that she actually has a fair amount of details about it, as opposed to some of the earlier conflicts.

With the spray done in this area, she continues along closer to the ground for the moment, figuring that with the sentient plants being as territorial as they are, they might not encounter one for a little while.]

It was caused by the bacteria, but they remained dormant in most people until set off by something external. In most cases, it was also music - a particular planet that had access to ancient technology to amplify a song that could trigger the shift took advantage of that for a while.