THE PLAGUE CYCLE

A long-view look at how viral and bacterial illnesses have influenced the course of human events.

The bad news is that today, heart attacks and strokes are the leading causes of death. The good news, writes development expert Kenny, is that this “is evidence of humanity’s greatest triumph: until recent decades, most people didn’t live long enough to die of heart failure.” Indeed, life expectancy has more than doubled around the world in the last 150 years, in part thanks to better diets and medical advances. The Covid-19 pandemic notwithstanding, infectious disease is not the devastating killer that it has been in the past, though it still kills plenty of people. The author charts the courses of those diseases, pegging their rising importance to the development of agriculture and the settling of humans in villages, towns, and cities, packed together to make a convenient target for such things as measles and cholera. “The more humans are loitering about,” writes Kenny, “the greater the chance of illness.” Some illnesses, such as trichinosis, have been all but eradicated, though in the case of that malady, Kenny hazards, it made for good enough reason for certain religious traditions to forbid the consumption of pork. New treatment methods, such as oral rehydration, have helped mitigate diarrheal diseases. Today, outside of Covid-19, many pandemic illnesses are lifestyle-related. As Kenny notes, these days, Chinese adults are about as likely to be obese as their American counterparts thanks to the availability of cheap processed food—and, he adds, “two out of five Earthlings have elevated blood pressure.” The downsides of the current pandemic are numerous, but, as Kenny demonstrates, revealing his developmental interests, the old Malthusian effects of plagues in reducing inequality no longer apply. Though the author’s popularizing approach is less scientifically rich than, say, David Quammen’s, it still stands in a long tradition of informative plagues-and-people books such as Hans Zinsser’s 1935 classic, Rats, Lice, and History.

A timely, lucid look at the role of pandemics in history.