There has often been a past history where an individual contracted an infection or spread it to others resulting in a karmic burden. Do pathogens have past karmic history and connection with people just like ETs and spirits?

In the same way that pathogenic microorganisms have consciousness, they also have karma. So the life they live as a kind of predator creates a karmic liability and a potential that is projected forward as a part of their existence energetically. It is the essence of why they are dangerous in being a pathogen causing harm to other beings. So that is a component of how they cause harm. Part is strictly biochemical and part is the karmic potential having harmful energy, adding negativity and making the spread to other victims more likely and more consequential in the rise of symptoms and continued presence, at least for a time, until they can be dealt with by the immune system.