Nonsense of Noah
Parasites and bacteria would have infested Noah and the Ark's inhabitants
Noah was specifically directed by God to bring aboard ..."every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female". Parasites and bacteria are living things of all flesh. They aren't flesh themselves, but if they are not on board, then they died in the flood and they wouldn't be here now. They are "of" the flesh.
Noah and family would have to tackle and complete their superhuman tasks (feed, water, muck stalls) while serving as living hosts for viruses, bacteria, fungi, and other microorganisms capable of producing pathologically based ailments in humans. A population of eight obviously had no chance to survive this fatal concoction of illnesses. If everyone had gone onboard disease-free, the microorganisms would have nowhere to thrive. Likewise, the animals carrying their own specific parasitic problems could not have realistically survived such turmoil.