🦠microbiology review

Justinian plague

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The Justinian Plague was a pandemic that afflicted the Byzantine Empire during the reign of Emperor Justinian I in the 6th century. It is caused by the bacterium Yersinia pestis, which also causes bubonic plague.

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5 Must Know Facts For Your Next Test

  1. The Justinian Plague began in 541 AD and recurred in waves until approximately 750 AD.
  2. It primarily affected the circulatory and lymphatic systems, leading to symptoms such as fever, chills, and swollen lymph nodes known as buboes.
  3. Yersinia pestis is transmitted through the bite of an infected flea that has fed on an infected rodent.
  4. The mortality rate during the initial outbreak is estimated to have been between 25% to 50% of the population in affected areas.
  5. The Justinian Plague significantly weakened the Byzantine Empire, contributing to its eventual decline.

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