They don’t think and they don’t control their mutations but selection acts on them and “chooses” the strains that reproduce more. Pathogens become less deadly w

They don’t think and they don’t control their mutations but selection acts on them and “chooses” the strains that reproduce more. Pathogens become less deadly with subsequent generations because those strains which kill the host quickly limit their spread. It’s not impossible for them to become more deadly but it is unlikely due to the fitness cost.