Final answer:
The Plague of Justinian, a likely bubonic plague outbreak, devastated the Byzantine Empire's urban population, with about one-quarter to one-half of the population in the eastern Mediterranean region dying from the plague.
Step-by-step explanation:
In the Byzantine Empire, the bubonic plague, particularly during the outbreak known as the Plague of Justinian from 541 to 750, had a catastrophic impact on urban populations. It is reported that in the eastern Mediterranean region, the plague eliminated approximately one-quarter to one-half of the human population. In Constantinople, at its peak, over 5,000 people died per day, amounting to roughly one-third of the city's population.
Mortality rates in major urban centers were staggering, with cities experiencing frequent outbreaks during successive pandemics. For example, Istanbul witnessed at least 230 outbreaks during the Second Pandemic, demonstrating the virulence and persistence of the plague in urban areas within the empire.