God gets absolved from creating diseases

One of the most common statements of the Christian theology is that before the so-called "original sin" there was no death nor disease, that they came after that. Many Christians are, in fact, very eager to absolve God from the responsibility of having created diseases that they will say things like diseases having been caused by our sins, not by God. (After all, no evil can come from God, so it has to come from somewhere else.)

That makes absolutely no sense. Are these people claiming that sinning is actually a creative force that can form things like viruses, bacteria and other kinds of pathogens, as well as the defects of the human biology that causes all kinds of diseases?

The viruses and other pathogens had to come from somewhere. If, according to Christian theology, God created everything, then he also created all disease. Trying to absolve God from this act, and blame humans of it, is nonsensical even from a Christian perspective.

(Even if we went through the path of partially admitting abiogenesis and claiming that disease simply formed on its own due to natural processes, and that God simply allowed it to happen "because of our sinning", that still hardly absolves God from having created the universe in such a manner that diseases could form, and allowing it to happen. Committing evil via negligence is as bad as committing it via more direct means. There's little philosophical difference.)

If, on the other hand, a Christian has the position that yes, God did create disease in order to punish us, then that only makes things worse. The entirety of humanity is punished for the sins of their ancestors. How exactly is this just and right? Why should you be punished for something that your extremely distant ancestor from thousands of years ago did?

(Note that disease can affect people of all ages. In fact, it can affect babies even before they are born. If the claim is that people get disease because they are sinful, then what they are effectively saying is that even unborn children are sinful, even before they become sentient in any way, for no cause of their own.)