New Books In Medicine Podcast: Dorothy H. Crawford Explains How Microbes Shaped Our History

Author: Dorothy H. Crawford

Book: Deadly Companions: How Microbes Shaped our History

New Books in Medicine is one of the podcast channels on the New Books Network, subscribe on iTunes or your favorite podcast software. 

Dorothy H. Crawford is a microbiologist, specializing in viruses who has written many popular science books. She’s always been fascinated by the interaction between microbes and man. She studies how that interaction has changed over the centuries. The term microbe, as defined in the book, refers to any microscopic organism including viruses, bacteria and protozoa.

While microbes have always existed, humans only discovered what they were around 130 years ago, and since then have found many ingenious ways to stop them from invading our bodies and spreading disease. Despite some remarkable success, old microbes are resurging and are still responsible for over 14 million human deaths per year.

The author wrote Deadly Companions about 10 years ago, and created an updated edition this year. She explores the cause and effect of some of the major epidemics in history such as the Plague of Athens, the Justinian Plague, the Black Death, and even SARS.

Listen below to Dorothy H. Crawford's thoughts about her book and learn more about how microbes shaped our history. 


Highlights from the Podcast:

1. Microbes first appeared on the planet earth around 4 billion years ago and have coexisted with humans ever since we evolved from our ape-like ancestors. These tiny creatures colonize our bodies and have profoundly influenced our evolution as a species by causing epidemics that have killed significant numbers of our predecessors they have also helped to shape our history.

2. On the different ways that various microbes spread:  spreading from host to host is the microbes lifeline. If an immunity builds up in one host and the microbes can’t find a suitable host to continue then the whole of that kind will die out. Microbes are very efficient at spreading and some of the ways include:

  • Direct or indirect contacts
  • Spread by air or water
  • Spread by blood like from a mosquito bite
  • Spread from mother to unborn child
  • Or some of the other common modern ways include blood transfusions, organ transplants, contaminated needles or surgical instruments.

3. An epidemic is defined vaguely as a large scale increase in a particular disease in a specific location. When a microbe is introduced to a naive or susceptible community it which can whip through the whole population until almost everyone recovers and  builds immunity or they die of the disease. A recent example is the Ebola virus.

4. 1.8 million years ago, there was a critical turning point when our ancestors moved from the rainforest to the open plains of east Africa and came into contact with herds of large game for the first time. The hominids were bitten by (sleeping sickness)  trypanosome-carrying tsetse flies, and as our ancestors became skilled game hunters the exposure to tsetse flies and parasites increased. In hunter-gatherer bands the big-game hunters were at greatest risk from the trypanosome. The strongest and most capable hunters in the band were the most likely to be suddenly struck down with sleeping sickness. Losing one or two of the best hunters in the early bands could have devastating effects for a small band of 50 people.

5. The biggest pandemic in recorded history is the Black Death which spread west from Mongolia in 1346 and reached the port of Caffa on the Black Sea in 1347. This trading post was where Europeans first began to notice the devastating disease, and the Italians attempted to flee it by boating to Sicily. The disease was then carried on to Genoa and Venice initiating the spread of the black death throughout trade routes in Europe, and North Africa, wiping out It one-third to one-half of the population in almost every town and village it spread to, this equates to about 20 million people.

In 1353 the plague ended, but outbreaks continued for 300 years, and had a great impact on the Europe. The Black Death microbes are spread by rodents— rats, in particular are susceptible to the infection and die rapidly. The fleas then get hungry and jump off the rats and onto humans which is how the plague spread so widely with the prevalence of rats following the trade routes along with the people.

What is This Book About?

Description from the back cover:

Ever since we started huddling together in communities, the story of human history has been inextricably entwined with the story of microbes. They have evolved and spread amongst us, shaping our culture through infection, disease, and pandemic. At the same time, our changing human culture has itself influenced the evolutionary path of microbes. Dorothy H. Crawford here shows that one cannot be truly understood without the other. 

Beginning with a dramatic account of the SARS pandemic at the start of the 21st century, she takes us back in time to follow the interlinked history of microbes and man, taking an up-to-date look at ancient plagues and epidemics, and identifying key changes in the way humans have lived - such as our move from hunter-gatherer to farmer to city-dweller -- which made us vulnerable to microbe attack. 


About the author, Dorothy H. Crawford

Dorothy H CrawfordDorothy H. Crawford has been Assistant Principal for Public Understanding of Medicine at the University of Edinburgh since 2007. She is author of the book Virus Hunt. Her previous books include The Invisible Enemy, Deadly Companions, and Viruses: A Very Short Introduction.

She lives in Edinburgh, enjoys gardening and writing popular science books. 



About the interviewer, Jeremy Corr

JeremyCorrJeremy Corr is a Sales Consultant who helps provider organizations grow revenue and create positive patient experiences. A University of Iowa history alumni, Jeremy is curious and passionate about all things healthcare, which means he’s always up for a good discussion!

Reach him at


About New Books Network

NBN MedicineThe New Books Network is a consortium of author-interview podcast channels dedicated to raising the level of public discourse by introducing serious authors to a wide public via new media.

They publish 100 new interviews every month and serve a large, worldwide audience. The not-for-profit, has over 800,000 downloads of their episodes a month. 


About Lisa Skriver

Lisa Skriver

Lisa has 8 years of experience working both front and back end revenue cycle. At MediRevv she has served both as a Patient Experience Representative and as a Revenue Cycle Representative, and today, she works as an Inbound Marketing Lead, sharing relevant content through a variety of channels to make connections with prospective clients. She enjoys videography and photography.

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