From Three Men in a Boat — Jerome K. Jerome

I remember going to the British Museum one day to read up the treatment for some slight ailment of which I had a touch—hay fever, I fancy it was. I got down the book, and read all I came to read; and then, in an unthinking moment, I idly turned the leaves, and began to indolently study diseases, generally. I forget which was the first distemper I plunged into, but before I had glanced half down the list of premonitory symptoms, it was borne in upon me that I had fairly got it. I sat for a while, frozen with horror; and then, in the listlessness of despair, I again turned over the pages. I came to typhoid fever—read the symptoms—discovered that I had typhoid fever. I had been suffering from it for months without knowing it. I came to the conclusion that I had every disease in the book except housemaid's knee.