2. The Justinian Plague killed 40% of the populations affected in 541-542 AD
The Eastern Roman (Byzantine) Empire was stricken by a plague which killed an estimated 25-50 million people in 541 AD. The pandemic struck hardest at Constantinople, and spread to various Mediterranean port, carried by ships involved in international trade. The ships also carried rats, infested with fleas which were the source of the disease. The pandemic spread from China across the Eastern Empire. Though its first wave lasted until late 542 AD, additional outbreaks occurred sporadically until well into the eighth century. The Byzantine historian Procopius estimated that 10,000 deaths occurred in Constantinople daily when the plague was at its height.
The weakened Byzantine Empire was unable to maintain the union with the Western Empire when the Lombards in Northern Italy invaded. Another historical impact of the plague was the settlement in Great Britain by Anglo-Saxons. Following the plague’s initial outbreak, grain prices skyrocketed in the Eastern Empire, as men strong enough to tend crops were scarce. The Byzantine Armies, hard-pressed by enemies from all directions, including Goths, Huns, Lombards, Persians, and Arabs, suffered a series of setbacks which shrank the empire. Justinian, for whom the plague was named, contracted the disease, though he survived.