The climatic pulse of Asia

Climate-driven plague outbreaks in Asia were repeatedly introduced into medieval Europe, new research from CEES, Norway, and WSL, Switzerland, shows.

Searching for rodent reservoirs of plague in medieval Europe, an interdisciplinary team of researchers from CEES at Dept. of Biosciences, University of Oslo and WSL, Switzerland discovered that the Black Death in 1347-1353AD and subsequent plague outbreaks in Europe were not –as is the prevailing view– the result of a singular introduction of Yersinia pestis from Asia. Their work, made possible by two EU grants (MedPlag, and PlagueEco2Geno) was published this week in the Proceedings of the National Academy of Sciences of the United States (Schmid et al.).

Rather than a rare one-time event with disastrous consequences for Europe's population – an estimated 30%-50% of Europe died in the first six years of the pandemic– they show that wildlife plague reservoirs in Central Asia played a crucial role for the dynamics of the plague in Europe. From the analysis of the largest dataset of medieval plague outbreaks compiled to date (7711 outbreaks), against 15 paleoclimatic proxies throughout Europe and Asia, a continuous, climate-driven process became visible. with new waves of plague repeatedly send across Eurasia into the Mediterranean harbors of medieval Europe.

Specific climate fluctuations that affect large areas of central Asia are known to start plague outbreaks within Asiatic plague foci, such as those inhabited by the great gerbil Rhombomys opimus. Boris Schmid and his co-authors observed that during the Second plague pandemic, similar climate fluctuations in Asia were followed by new waves of plague arriving first in southern Russia, and then into European harbors, with a delay of 15±1 years. Likely, in each of these waves, plague outbreaks in one of Asia's natural rodent reservoirs reached the trade routes, and spilled over into human civilization.

The infamy of the Black Death1 makes plague a fascinating topic for many. Its history is currently being rewritten largely thanks to newly available genetic material of ancient (Haensch et. al.2) and contemporary origin (Cui et al.3), which starts to shed light on how the bacterium moved across the globe. Importantly, in this work, scientists have expanded the role of the wildlife reservoirs of plague from one-time initiators of a devastating pandemic, to a continuous, climate-driven source of plague. In addition, it challenges the long-standing, but poorly substantiated view that the bacterium Yersinia pestis must have had a permanent European wildlife reservoir of plague, such as the urban black rat4. Instead, new strains of the disease would frequently be imported from Asia.

Contact person: Nils Chr. Stenseth
phone: +47-22854584/+47-22854400

Research professor of Ecology and Evolution at Department of Biosciences, University of Oslo (
Chair of CEES (
Chair of NorMER (
President of the International Biological Union (IUBS:
Member of the Scientific Council of the The European Research Council (ERC:

  1. Stenseth, NC, et al. "Plague: past, present, and future." PLoS Medicine 5.1 (2008)
  2. Haensch, Stephanie, et al. "Distinct clones of Yersinia pestis caused the black death." PLoS pathogens 6.10 (2010)
  3. Cui, Y, et al. Historical variations in mutation rate in an epidemic pathogen, Yersinia pestis. Proceedings of the National Academy of Sciences, 110.2 (2013)
  4. Hufthammer, K, Walløe, L. Rats cannot have been intermediate hosts for Yersinia pestis during medieval plague epidemics in Northern Europe. Journal of Archaeological Science, 40 (2012)
Published Feb. 23, 2015 9:01 PM - Last modified Feb. 24, 2015 8:09 AM