Volcanism and global plague pandemics : towards an interdisciplinary synthesis.

Understanding the prevalence and dissemination of bacterial pathogens such as Yersinia pestis, the bacterial agent of plague, is key to identifying the origins and demographic impact of historic pandemic episodes and mitigating future risk. Climate may influence the spread of Yersinia pestis through impact upon bacterial, vector, and rodent host populations prior to human infection. Large climate-forcing volcanic eruptions have the potential to influence global climate for several years following the eruption with evidence increasingly suggesting that, through oceanic feedback mechanisms, some eruptions can influence climate for decades to centuries. This article assesses the potential mechanistic links between some of the largest volcanic eruptions of the Common Era and the three recorded plague pandemics. The article uses proxy records of climate and volcanic forcing along with historic data to suggest mechanisms by which each of the pandemic episodes may have been influenced by volcanism. Commonalities between the pandemic episodes are surprisingly rare, but it is suggested that the influence of volcanism on climate may be an important factor and may aid in understanding the complex array of factors which caused plague pandemics