Question about Salmonella

[Navotifarm]

The thread about news media is also about the salmonella in the mind+-boggling number of eggs. I have not seen ANY tv since the switch from analog so the best reference I've had so far was the link to information about NIH plus what was posted here. From my own experience, I once visited a chicken-raising farm when I was seeking to invest in land and this was a going business. I am an asthmatic. I was terribly sick for days. The dust from the feed plus particles from dried manure and feathers was overwhelming. They did have big exhaust fans going which stirred the air.
So I am looking for connection and explanation here from someone who actually knows. Salmonella is bacteria, right? That was on spinach and peanuts (exterior) and now it is inside chickens who seem to be healthy enough to function as egg layers but the eggs have salmonella INSIDE them. They probably have it outside too but they are washed and disinfected.
What I would like to know is, where is all this salmonella coming from? Well, actually I would like to know more as in a whole picture from a reliable source.
As a court reporter I did many meetings and hearings when. SAIDS was first discovered ( S for simian meaning monkeys brought into labs for experimental purposes) which then morphed to humans. I worked with many gay men who were all killed by aids in the early years. As a visual person I see connection between salmonella, equine encephalitis, salmonella, bird flu, pig flu etc. Maybe there isn't any scientifically.
However, there is confusion and curiosity in my mind. Perhaps somebody here is knowledgeable and can clear away some of the mind murk with some accurate facts?