"There is no us and them"

Our adaptive immune system, the branch of our immune system that develops long-lasting immunity, is thought to have been borrowed its essential technology from the DNA of a virus. Some of our white blood cells recombine their genetic material like random number generators, shuffling genetic material like random number generators, shuffling their sequences to create an immense variety of cells capable of recognizing an immense variety of pathogens. This technology was viral technology before it was ours. Of humans and viruses, Carl Zimmer observes, "There is no us and them."

from On Immunity by Eula Biss (2015)