But however secure and well-regulated civilized life may become, bacteria, Protozoa, viruses, infected fleas, lice, ticks, mosquitoes, and bedbugs will always lurk in the shadows ready to pounce when neglect, poverty, famine, or war lets down the defenses.

Infectious Disease is one of the few genuine adventures left in the world.

But however secure and well-regulated civilized life may become, bacteria, Protozoa, viruses, infected fleas, lice, ticks, mosquitoes, and bedbugs will always lurk in the shadows ready to pounce when neglect, poverty, famine, or war lets down the defenses.

Our task as we grow older in a rapidly advancing science, is to retain the capacity of joy in discoveries which correct older ideas, and to learn from our pupils as we teach them.

[I]nfectious disease is merely a disagreeable instance of a widely prevalent tendency of all living creatures to save themselves the bother of building, by their own efforts, the things they require. Whenever they find it possible to take advantage of the constructive labors of others, this is the path of least resistance. The plant does the work with its roots and its green leaves. The cow eats the plant. Man eats both of them; and bacteria (or investment bankers) eat the man.

We have chosen to write the biography of our disease because we love it platonically - as Amy Lowell loved Keats - and have sought its acquaintance wherever we could find it. And in this growing intimacy we have become increasingly impressed with the influence that this and other infectious diseases, which span - in their protoplasmic continuities - the entire history of mankind, have had upon the fates of men.

Throughout the early Christian period, every great calamity - famine, earthquake, and plague - led to mass conversions, another indirect influence by which epidemic diseases contributed to the destruction of classical civilization. Christianity owes a formidable debt to bubonic plague and to smallpox, no less than to earthquake and volcanic eruptions.