SO VERY SMALL

A detailed history of germ theory and how its emergence changed the world.

Levenson, a professor of science writing at the Massachusetts Institute of Technology, begins this very enjoyable and informative read with the arrival of the bubonic plague in 17th-century London, as reported in Samuel Pepys’ diary and the medical records of the time. Doctors had no scientific foundation for understanding its cause and thus no way to deal with it. A clue came when Dutch cloth merchant Antonie van Leeuwenhoek used an advanced (for the day) microscope to observe tiny creatures, now known as microbes. But the idea that they might cause disease went against all received doctrine. Such miniscule creatures should be unable to harm human beings, who were on top of the natural order. It took a good 200 years more before Louis Pasteur and Robert Koch used careful scientific research to make the case that germs did, in fact, cause disease—and that they could be countered by vaccines. Another generation passed before scientists developed chemicals to kill germs that infected animals or people. By the late 1940s, penicillin was in regular use, and the war against infectious disease appeared to have been won. But that sense of triumph didn’t take into account the microbes’ ability to evolve their own defenses against the antibiotics—and suddenly the apparent victory is looking much more tenuous. Levenson gives a good account of the vigorous competition between the early advocates of germ theory as well as the often-heated battles with their opponents, paying due attention to the traditional ideas those opponents held. And his research turns up some surprises; for example, an early champion of smallpox vaccination was Cotton Mather, better known for his persecution of “witches” in colonial Massachusetts.

An engaging survey of the discovery of microbes, their role in disease, and the efforts to combat them.