What are the four stages of human diseases?

Look at Table 11.i in the book, in which Diamond discusses how humans have historically picked up diseases from the animals they have domesticated, as well as wild animals, and how these diseases progress in humans. His four stages explicate the stages of "evolution of a specialized human disease from an animal precursor."
The first stage, according to Diamond, is illustrated by the many diseases that humans can pick up from pets and domesticated (e.g., farm) animals. The examples Diamond gives include cat scratch disease from cats and brucellosis from cows. We can also pick up diseases from wild animals, provided we're in contact with them.
The second stage is when a "former animal pathogen evolves to the point where it does get transmitted directly between people," causing epidemics. Diseases at this stage, however, will die out at a certain point, either because medicine has cured them or everyone has already had the disease and developed an immunity to it.
Pathogens which do not die out reach the third stage. These are pathogens which can become "killers of humanity" because they have not been eradicated, as most pathogens are, at the second stage.
Diseases which progress to the fourth stage have successfully evolved to a point where they are well-known and continuous diseases which are able to continuously adapt to resist being wiped out. Diseases at this stage have become limited to humans, have developed human-specific strains, and are sufficiently advanced in their evolutionary capacities that they can go on adapting to find better and better ways to survive and thrive.

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