In 541, a previously unknown disease broke out in the Egyptian town of Pelusion. People initially came down with a mild fever, but the sick soon also developed swellings in the armpits. Some people fell unconscious, others went manic, some were covered with black blisters and died soon after, and in others, the blisters began to ulcerate. If people recovered, they sometimes suffered speech problems or numb limbs.
The epidemic spread rapidly. From Egypt it travelled inland via the coasts and eventually reached Constantinople, where it raged for about four months. The historian Prokop mentions at first 5,000, then 10,000 and more daily deaths. He described the dramatic situation: “There were not enough living souls to bury the dead. People barricaded themselves inside their houses. When one saw a person in the street still alive, it was someone carrying a body.” John of Ephesus, who was travelling in the Empire during that time, describes abandoned villages and dead cattle in the fields, and he feared that he himself would soon fall victim to the disease.