wonder no more. The good people of AiG have the answers.
I particularly like this part
First, we must restate that God created all microorganisms. Even though the word germ does not appear in Scripture, that does not mean that God didn’t create them. Many other modern words such as trinity, dinosaur, or Pixar are not in the Bible but we know that they exist. Bacteria were created early in Creation Week and were part of what was pronounced “very good” . Due to Adam’s sin, all of creation was cursed to varying degrees; the genomic deterioration of microbes began at that time. We cannot know for certain that microbes immediately became pathogenic and began to kill living things right after the Fall, but we do know that the origin of “molecular” thorns and thistles could have happened at that time because of the thorns and thistles on plants.