Thanks difficult to answer. I’m not sure I know the answer. I can say that I’m interested in a theory that we are all genetically programmed to acquire any disease but something triggers it in different individuals.
I don’t think that we know exactly. For some it is easy – like genetic diseases such as cystic fibrosis. For others, like cancer and diabetes, it is a constellation of factors that we don’t fully understand – genetics may enhance risk but still don’t seem to fully determine whether you actually develop the disease, triggers like lifestyle/environmental factors seem to play a role. Even for infectious diseases caused by bacteria/fungi/viruses, for most pathogens just because you are exposed it doesn’t mean that you will necessarily become infected, it may depend on your health status, immune system, perhaps even your microbiome.