The lack of reliable demographic data for Byzantine cities raises questions as to the actual
rate of expansion and mortality of plague. This essentially leads to the question of change and
progress of the nature of infectious diseases in that period. Also the analysis of the written
sources raised a series of questions mainly epidemiological in nature: the entry points and
spreading of the disease in the Mediterranean the epidemic dynamics as well as the evolution
of the microbial agent of plague i.e. Yersinia pestis. The present study offers a substantial
explanation for the outbreaks of plague that struck Byzantium by exploring the multiple factors
that caused or triggered epidemics. The study covers the entire period extending from the
beginning of the Byzantine Empire until its fall in 1453 which was marked by two major
pandemics namely the Plague of Justinian and the Black Death. All known primary sources were
collected and grouped from a spatiotemporal perspective so as to retrace the unfolding of the
two pandemics. The focus of the research shifts from known historical frameworks to ones of
human activities endemic foci and natural environment of the era as risk factors of the
outbreaks.
