Rereading a classic: "Rats, Lice, and History," by Hans Zinsser
It is hard to imagine that a doctor who treated typhus epidemics during and after the First World War would ever produce a book with such an entertaining, sometimes whimsical tone. The author, William Zinsser, as an undergraduate at Columbia was torn between a career in a lab or in letters, and he went on to straddle both. Later, at Harvard he taught epidemiology and contributed poetry to the Atlantic.
He gained first hand knowledge of typhus epidemics on public health missions after the First World War in Eastern Europe. In Russia alone, typhus claimed several million lives. When Rats, Lice, and History was published in 1935, it topped US bestseller lists and has remained in print ever since. The science in it may have dated, but the author’s approach has not. The reader is three quarters through the book before typhus becomes the main subject. Think epidemiology infected by Tristam Shandy.
A virus is elusive, anonymous, nearly invisible. But every virus has a life of its own and as such has a biography: a time and place when it was born, formative influences that shaped its youth, and things it gets up to after growing up and going out into the world. And a virus has a wider family that has kept company with humanity from time beyond memory.
Epidemics are products of history. And the way humanity thinks about epidemics is historical too. From antiquity until the Renaissance there were two ways epidemics were looked at. The Old Testament explained epidemics as a scourge inflicted by divine will; Hippokrates laid out observations of symptoms and his tract Of the Epidemics. A third approach that looked for links between individual cases occurred in the sixteenth century. A medic in Verona, Fracastro, paved the way for public health policies based on science. In De contagione he surmised that infections could be spread through intermediaries, such as clothing. Pre-Fracastro, puzzled doctors could do little more than map the spread of epidemics. Post-Fracastro, doctors started looking for barriers to stop them.
Epidemics by then had determined the outcome of many of the wars on which world history had pivoted. On balance, viruses held a bias in favour of defenders: invaders spent extended periods in crowded camps where poor sanitary conditions exposed them to infections. Had it not been for epidemics, Athenians might have been overrun twice, by Persians and by Spartans; Sicily would have been wrested from Rome by the Carthaginians; Mecca would have been razed by Ethiopians: the lives of Perikles, Scipio, and Muhammad would have been very different. Epidemics wasted the armies of Justinian, of Frederic Barbarossa, and of Napoleon. In the Civil War and the First World War, American armed forces suffered more casualties in hospitals than in battle.
If war-borne epidemics discriminated against invaders, trade-borne epidemics were even-handed. Exploration of the Americas opened up seaborne transmission of viruses across the Atlantic in both directions. The New World was gifted typhus, and it sent back a disease to Europe in return: syphilis. Zinsser surmises that syphilis had been virulent in the Americas for centuries and its effects had weakened as native populations had developed resistance – herd immunity, in today’s parlance. As viruses have mutated over time, so have the organisms that hosted them, human or otherwise. The impact of typhus and of syphilis was at its most ferocious on victims whose organisms were without defence.
Rats, Lice, and History purports to be about typhus. But Zinsser’s broad sweep tells us that if typhus is the subject of the book, his theme is much wider and his message much deeper. A virus is a parasite, forever hunting for hosts, capable of protean changes in its quest to survive. It is both an agent of change and of evolution. Thus all organisms act as parasites: plants on the earth, animals on plants, humans on animals and viruses on all. If the viruses of yesteryear have lost their force as other organisms soaked them up, then for as long as organisms interact in new ways there will be new ones ever incubating. Rats, Lice, and History is a genre-bending book, biology as history and history as biology. In nature, there is no end to history.
