Gerbils from Asia Spread the Plague to Europe

When we heard the term bubonic plague, we immediately think of the Black Death that ravaged Europe in the fourteenth century. Scholars have acknowledged that the contact along the Silk Road contributed to the spread of the plague across the Eurasian continent in the fourteenth century. The prevailing theory is that the fleas on rats in populated areas caused the repeated outbreaks of plague after the Black Death. Recent evidence suggests that the later epidemics came from gerbils found in Asia.

After the Black Death made its way through Europe, several subsequent outbreaks lasted from the late fourteenth century to the nineteenth century. Previously, scientists connected them to rats living in Europe, but there was always the question of why the plague would go away and start up again. Using over 4,000 historical records, researchers from the University of Oslo traced sixty initial epidemics in port towns, such as Hamburg, London, and Barcelona, which spread to smaller areas nearby.

With warmer climate change, reproduction in small rodents and fleas increases, which was thought to spread the plague after the end of the 14th century. The researchers tracked the years of the initial outbreaks in the port towns, which were sixteen isolated incidents between the fourteenth century and the nineteenth century. Researchers couldn’t find any significant climate changes in Europe that would account for the spread of the plague. However, when they analyzed climate data in Asia, they found substantial temperature drops that would cause less flea and rodent reproduction fifteen years before the new outbreaks in Europe.

According to the study, as the rodent population decreased, fleas spread to the camels commonly used in trade along the Silk Road, and then the fleas spread to people. The plague then moved along the trade routes over a time span of fifteen years, until it emerged in Europe through contact with traders that came to European ports. This new research rejects the theory that the fleas on rats spread the plague in Europe’s major cities, explaining the reintroduction of plague in cities that had no significant rat population. It also completely changes what we thought about the spread of disease along the Silk Road.