
While human beings may consider themselves to be "master of the earth," Preston argues that nature has the ultimate power, even to the point of determining the course of human evolution. The power of nature is a recurring theme in Preston's descriptions of the various outbreaks of Marburg and Ebola.

In the meantime, the role played by both chance and human error will be even more significant in determining the path of a potential outbreak.
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Ultimately, until science and knowledge can catch up with the filoviruses, there is no option but for individuals like Nancy Jaax and Gene Johnson to continue their research. Preston notes that only three of the seven proteins in filovirus strains have yet to be identified, while even the mystery of Kitum Cave and the source of the Marburg virus is still far from being solved.

Yet, as Preston reveals, their knowledge of filoviruses is woefully incomplete, especially when it comes to their ability to create a preventative vaccine or cure. The majority of the main characters in the book are highly-trained scientists and medical personnel with significant experience with hot agents.
