On Immunity: An Inoculation

by Eula Biss

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 minuscule 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 ou...