Many will consider the answer to the question posed in the title of this post obvious, as indeed do I: The Bible does not contain superior medical knowledge, or indeed anything that we might consider medical knowledge in the modern sense at all, because it was written before there was any medical knowledge, much less advanced medical knowledge.
But I ask the question anyway to highlight this point for the benefit of young-earth creationists and others who claim that the Bible contains scientific knowledge more advanced than human beings had achieved in the time these texts were composed.
If that were so, we should expect them to include other sorts of more advanced knowledge, such as in the realms of medicine, health, and hygiene.
Yet you will look in vain in the pages of the Bible for a recommendation that people cover their mouth and nose when they sneeze and cough. You will find mentions of strong drink, but nothing about distilling the alcohol and using it to clean wounds or disinfect anything at all. Nor will you find the Bible’s authors recommending that drinking water be boiled to kill dangerous bacteria.
Answering the question of why these things are not in the Bible is simple, if one has a view of the Bible that is realistic, and based on what the Bible shows itself to be. In those times they didn’t know about germs, about viruses or bacteria, and thus neither mention them nor offer a means of avoiding their harmful effects (although they do occasionally mention the “angel of death” in such places where we might mention outbreaks of disease).
And so I offer this as one more argument for accepting the Bible as it is, rather than trying to pretend that it is something it is not.