Can’t Live With Them, Can’t Live Without Them
How the fear of germs can be as infectious as a disease
An excerpt from ‘On Immunity’
“We talked about germs in school,” my son told me after one of his first days of preschool. The pronoun and the past tense made this a challenging sentence that had taken him several minutes of silence to formulate. He was holding a “germ” constructed of tangled and tortured pipe cleaners that looked not entirely unlike the electron microscope photos in the immunology textbooks I paged through while he was in school. “What did you learn?” I asked. “Germs are really, really tiny and really, really dirty,” he explained with enthusiasm, happy to share his new knowledge. “Yes,” I agreed, “that’s why we have to wash your hands when we get to school in the morning, to wash off the germs so they don’t get on anyone else.” He nodded gravely, “Germs can make you sick. Make you cough.”
The conversation ended there, in part because my two-year-old had, in the span of a few simple sentences, completely articulated my entire knowledge of infectious agents. It was a sobering moment. Sometime after this exchange, I looked up germ in a medical dictionary and was reminded that the word is used in two ways. A germ is an organism that causes disease, or it is a part of the body capable of building new tissue.
We use the same word for something that brings illness and something that brings growth. The root of the word being, of course, seed.
We need germs. Without exposure to germs, we now know, a child’s immune system is prone to dysfunction. In 1989, the immunologist David Strachan proposed that having older siblings, belonging to a large family, and living in an environment that was not overly sanitized might help protect children from developing asthma and allergies. This “hygiene hypothesis” suggested that it was possible to be too clean and too free of disease.
As the hygiene hypothesis took hold, scientists searched for one particular childhood disease that might prevent allergies, but this thinking gave way to the understanding that the overall diversity of germs in our environment is probably more important. In 2004, the microbiologist Graham Rook proposed an “old friends hypothesis,” in which he suggested that a healthy immune system is not achieved through childhood diseases, which are relatively new, but through exposure to ancient pathogens that have been with us since our hunter-gatherer days. These “old friends” include parasites and worms as well as the bacteria that colonize our skin, lungs, nose, throat, and gut.
The hygiene hypothesis is still sometimes interpreted as a reason not to prevent infectious disease. “For all we know,” as a friend remarked to me, “diseases like measles may be essential to our health.” But the native peoples of the Americas lived for millennia without measles until it was introduced to this hemisphere relatively recently, with devastating results. And even if we eliminate measles through vaccination, as is theoretically possible, an abundance of germs remain. There are, for instance, about a million different viruses in a teaspoon of sea water.
We may not muck around with other organisms as much as we should, but we have no dearth of germs available to us on earth.
Vaccination of humans has made one single virus extinct—the variola virus that causes smallpox. But novel viruses are constantly inventing themselves, as viruses have a special talent for genetic variation. Of all the varieties of germs, viruses may be the most vexing. They are mysterious creatures, parasitic and vampiric by nature. They are not exactly inanimate, but viruses are not, strictly speaking, alive. They do not eat, do not grow, and generally do not live in the manner that other living things live. Viruses must enter and inhabit a living cell in order to reproduce, or to do much of anything. On their own, they are little more than miniscule bits of inert genetic material, so small that they cannot be seen by an ordinary microscope. Once inside another cell, viruses use that cell’s body to make more of themselves. The metaphor of a factory is often used to describe how viruses work—they enter a cell and force its equipment to produce thousands more viruses. But viruses strike me as more supernatural than industrial—they are zombies, or body snatchers, or vampires.
A virus can, on occasion, infect an organism in a way that ensures the viral DNA will be passed on to that organism’s offspring as part of their genetic code. A rather surprising amount of the human genome is made up of debris from ancient viral infections. Some of that genetic material does nothing, so far as we know, some can trigger cancer under certain conditions, and some has become essential to our survival. The cells that form the outer layer of the placenta for a human fetus bind to each other using a gene that originated, long ago, from a virus.
Though many viruses can not reproduce without us, we ourselves could not reproduce without what we have taken from them.
Our own adaptive immune system, the branch of our immune system that develops long-lasting immunity, is thought to have borrowed its essential technology from the DNA of a virus. Some of our white blood cells combine and recombine their 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, the science writer Carl Zimmer observes, “There is no us and them.”
On Immunity: An Inoculation is available now from Graywolf Press.
Excerpt from On Immunity: An Inoculation, copyright (c) 2014 by Eula Biss. Reproduced with the permission of Graywolf Press, Minneapolis, Minnesota,
www.graywolfpress.org.
Photo Credit: Photo of diverse E.coli bacteria by Mattosaurus exists in the public domain.
Eula Biss is the author of Notes from No Man’s Land, winner of the Graywolf Press Nonfiction Prize and the National Book Critics Circle Award in criticism, and The Balloonists. Her essays have appeared in Harper’s and the Believer, and in The Best American Nonrequired Reading and The Best Creative Nonfiction. She has received fellowships from the Guggenheim Foundation, the Howard Foundation, and the National Endowment for the Arts, and she has won the 21st Century Award from the Chicago Public Library Foundation. Biss teaches at Northwestern University and lives in Chicago.
