To me. In a number of my books for some reason i go back to the same characters of nonfiction so i think i may be one of the only nonfiction writers i know of who has a repertory cast. Peter jahrling for example the guy the swift ebola virus and the hot zone he said whiffing ebola virus from a flask was the second dumbest thing you did it. The dumbest thing hes ever done is to tell Richard Preston zubaydah. Peter is a good friend of mine and he has come back again and again. He has been a demon in the freezer or major character. He was a source for two of my books without being in the foreground and im now at work on another book and i think peter will be back in that one as well. In all this is a long way to answering your question. Its a matter of taking notes and getting to know my subjects. In this case i did not go to west africa. I did all of my reporting at m. I. T. And also at an nih laboratory in maryland that i never went to africa. I will be going to africa through the cours