Transoceanic pathogen transfer in the age of sail and steam

What is it about?

In 1492, Christopher Columbus’s pioneering journey across the Atlantic opened a new era in global pathogen exchange. Sail and, later, steam ships spread diseases across the world — often with devastating consequences for local populations. These new technologies transformed global infectious disease — but their impact wasn’t immediate. Measles may have arrived in the Caribbean in the 1490s, but it was not until the mid-1800s that the virus first spread across the Pacific. Our study investigates why it took so long for infectious diseases to spread across the world. Using mathematical modeling, we show that the long travel times of sail and steam ships limited how easily diseases could spread. In small ship populations, diseases often ran out of people to infect and went extinct before the end of a voyage, leaving no infection to introduce. Diseases tended to survive longer on ships with larger and more vulnerable populations, which increased the risk of spreading across oceans. Using data from Gold Rush-era San Francisco, as historical voyages 1492-1918, we show that journey times and population sizes likely had significant impacts on the timing and frequency of infectious disease transfers across the world.

Featured Image

Photo by Austin Neill on Unsplash

Photo by Austin Neill on Unsplash

Why is it important?

Centuries before present-day air travel, sail and steam ships introduced diseases to new parts of the world. However, this process wasn’t immediate. Global spread of fast-burning pathogens like measles, smallpox, and influenza, required fast journeys and large-scale movement of people. Understanding this gives us a new perspective on epidemics, pandemics, and human history.