Great Spring Sickness
From A Wiki of Ice and Fire
The plague killed tens of thousands in the Seven Kingdoms with the major cities affected the most; it was bad in Lannisport, worse in Oldtown, but worst of all in King's Landing, where four in ten succumbed to it.} A strong man could wake up healthy in the morning and die by the evening, so swiftly did the plague strike.
Dorne and the Vale of Arryn did not suffer from the Great Spring Sickness, as they closed off their access roads and their ports to all travellers. Duncan the Tall and his squire, Egg, were in Dorne for the duration of the plague so were unaffected by it.
The plague did not care for status and killed people high-born or low, including King Daeron the Good, his last Hand of the King and his two most immediate heirs, Princes Valarr and Matarys, as well as the High Septon, a third of the Most Devout, and nearly all of the silent sisters in King's Landing.
Lord Brynden Rivers, the Hand of the King to Daeron's successor Aerys I Targaryen, ordered the many bodies be brought to the Dragonpit and burned by the pyromancers. The light of their wildfire pyres could be seen as a dark green glow throughout the city during the night. Others known to have died of the Sickness were Rolland Uffering, 4th husband of Lady Rohanne Webber, Lord Damon Lannister and the heir and eldest son of Lord Bracken.
|“||A dreadful time, ser, dreadful.||”|
|“||By the end, half the city was praying to the Stranger.||”|