Once again, you don't get it. Let's suppose that I feel completely fine and healthy. I have no problems physically. Yet I go in for a chance blood work and soon the doctor calls me on the phone.
"I've got some bad news," he says.
"What's that?"
"You're HIV positive."
"So what?"
"It means you're sick."
So let me get this logic straight. Even though I feel fine, and have no symptoms, I have a disease because microorganism (x) was found in my bloodstream. This is proof, I suppose, that microorganisms cause disease.
Sounds circular to me.
Of course you can also have diseases without microorganisms. Cancer springs to mind.
Strangely enough, often the way to prevent yourself from getting a disease with microorganisms is to infect yourself with microorganisms. This is called "vaccination."
I also note that "Scurvy is a disease caused by a diet that lacks vitamin C..."
What is scurvy? What causes scurvy? - Medical News Today
In short, I think your claim is a little too broad.