If reproduction of itself is why pathogens infect hosts, wouldn’t it be best for them to infect and keep the host alive rather than causing death? Do they just reproduce too much and kill the host without understanding that it would result in the host dying and themselves with it?
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Most human-adapted pathogens usually don’t kill the host; they evolved to use the host to reproduce without killing it. Those that do kill the host usually jumped from another species and managed to survive in humans to spread (like tuberculosis coming over from cows). The pathogen does what would just make a cow sick but happens to kill a human. If there is enough of a human population that doesn’t die and can pass it on for long enough, the pathogen will eventually adapt to kill humans less and less as the mutations that survive longer can get passed on easier. This is why the 1918 influenza, which killed 50-100 million people (about 1-2% of the infected healthy adults) has mutated into the modern ‘flu’ which will kill less than 0.05% of healthy adults.
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