Writers love disease. It fulfills all sorts of useful functions; it can be used to investigate fictional characters, and even give them a greater depth and nobility (e.g. ‘The Magic Mountain’ by Mann). It can act as a metaphor for societal problems (think of ‘The Plague’ by Camus). Illness is not allowed to be itself.
It’s not just writers who like this way of thinking. It seems to be ubiquitous. But this attachment of metaphor to illness is very pre-science. TB was thought to favour sensitive, artistic souls, until Koch’s discovery of the relevant bacterium. Cancer doesn’t have a simple one-size-fits-all cause or cure, so people speculate that it can be associated with, or caused by, repressed feelings, and cured by having a positive attitude.
In her famous essay ‘Illness and its Metaphors’, Susan Sontag criticised the widespread use of military metaphors in the discussion of cancer. Implicit in many descriptions of life with cancer is the assumption that if you don’t battle against the disease you are surrendering, and must bear the blame if the disease wins. She pointed out that many major illnesses have their own set of distinct metaphors, and what these metaphors really tell us about is our attitude to the illness, not the illness itself.
The metaphors get more complicated when the boundaries of the illness itself get fuzzier. What if we discover we are carriers of an illness that hasn’t actually caused any symptoms – yet? What if an illness runs in our families but no one’s yet found any relevant gene that could be deemed to be a cause? Are we ‘ill’ in either of those circumstances?
Illness has an extra dimension now; the dimension of time. And a new grammar to describe it; the grammar of the possible, and the subjunctive.
The commonly used metaphor for genes’ potential to cause illness is a ‘timebomb’ waiting to go off; something external buried deep within ourselves that is primed to explode at an time unknown to us. This ‘timebomb’ is another use of the military metaphor, and as with cancer, externalises the cause of the illness in a way that is essentially incorrect. Genes are not external forces (although they may, or may not, act according to external forces). They are part of us, they help define us.
We can behave in ways that may lessen the probability of us developing an illness (note that I don’t use the word ‘protect’ – another metaphor from the battlefield) but we are our illnesses as well as our health. We can’t own one without the other.
We need to develop new metaphors.
 Actually, cause and effect get jumbled here. TB was also thought to make the sufferer more pre-disposed to an artistic temperament if they weren’t already so inclined.