The bloody flux's symptoms are fever, intestinal hemorrhages, and bloody diarrhea.
It is a well-known disease, with little treatment beyond prevention (mainly quarantine and avoiding contact with carriers). It has a very high mortality rate, and may kill three out of four men in a city. Ser Barristan Selmy states that the bloody flux has been the bane of every army since the Dawn Age, and that he has known the bloody flux to destroy whole armies when left to spread unchecked. Even hard men like the Second Sons are terrified of "mounting the pale mare," and they will drive out anyone suspected of having the disease without a moment's hesitation.
A Clash of Kings
A Storm of Swords
A Dance with Dragons
A dying Astapori rider arrives in Meereen atop a pale mare, warning that Astapor is burning. He is brought to the Temple of the Graces by the Unsullied, and though the Blue Graces treat him for an arrow wound, he dies within an hour. The Blue Grace Ezzara tells Daenerys that the man's fever was not from his wound, but that he had soiled himself many times, with blood in his stool. The Green Grace, Galazza Galare, warns Daenerys that the man has been sent by the gods as a sign. Daenerys is initially dismissive of her words, but then connects the rider to Quaithe's warning, and becomes increasingly concerned.
The bloody flux is brought in numbers to Meereen by the Astapori refugees that seek protection in that city. Warned about the dangers of letting the refugees in, Daenerys decides to forbid their entrance, but allows them to camp outside the city, and sends them healers. However, the bloody flux is already spreading, killing a hundred men a night, and ravages both Meereen and its besiegers from Yunkai and New Ghis. The disease becomes known as "the pale mare", after its harbinger.
In the Yunkish camp outside Meereen, the enslaved Tyrion Lannister helps tend to his overseer, Nurse, when the man becomes sick with the pale mare. Tyrion feeds Nurse soup, allegedly to rehydrate him, but Tyrion puts poisonous mushrooms in the broth, and Nurse dies. When their master, Yezzan zo Qaggaz, also becomes ill with the pale mare, Tyrion, Penny, and Jorah Mormont are able to escape their captivity, finding safety with the Second Sons. Tyrion worries that Penny, who is sleeping a lot and claims to be tired, may be sick. However, he does not dare to ask if she is feverish, since he knows the Second Sons would drive her away in a moment if they thought she had the pale mare, and perhaps return all three of the escaped slaves to Yezzan's heirs.
In the Dothraki Sea, Daenerys becomes sick with vomiting, diarrhea, and fever. However, since the symptoms came upon her weeks after she left Meereen, they are probably not because of the pale mare, but due to the likely poisonous green berries she ate immediately before she became ill.
Galazza: We must pray. The gods sent this man to us. He comes as a harbinger. He comes as a sign.Daenerys: He was one man. One sick man with an arrow in his leg. A horse brought him here, not a god. A pale mare.
Daenerys: A sign of what?
Galazza: A sign of wroth and ruin.
She had sent them healers, Blue Graces and spell-singers and barber-surgeons, but some of those had sickened as well, and none of their arts had slowed the galloping progression of the flux that had come on the pale mare. Separating the healthy from the sick had proved impractical as well. Her Stalwart Shields had tried, pulling husbands away from wives and children from their mothers, even as the Astapori wept and kicked and pelted them with stones. A few days later, the sick were dead and the healthy ones were sick. Dividing the one from the other had accomplished nothing.—thoughts of Daenerys Targaryen
From here he could see four lesser pyramids, the city's western walls, and the camps of the Yunkishmen by the shores of Slaver's Bay, where a thick column of greasy smoke twisted upward like some monstrous serpent. The Yunkishmen burning their dead, he realized. The pale mare is galloping through their siege camps.—thoughts of Barristan Selmy
—thoughts of Tyrion Lannister
Behind the Scenes
- Dictionary.net: Bloody flux
- A Dance with Dragons, Chapter 55, The Queensguard.
- A Dance with Dragons, Chapter 36, Daenerys VI.
- A Dance with Dragons, Chapter 30, Daenerys V.
- A Dance with Dragons, Chapter 66, Tyrion XII.
- The World of Ice & Fire, The Reach: Andals in the Reach.
- Fire & Blood, The Long Reign - Jaehaerys and Alysanne: Policy, Progeny, and Pain.
- A Clash of Kings, Chapter 41, Tyrion IX.
- A Storm of Swords, Chapter 57, Daenerys V.
- A Dance with Dragons, Chapter 11, Daenerys II.
- A Dance with Dragons, Chapter 25, The Windblown.
- A Dance with Dragons, Chapter 57, Tyrion XI.
- A Dance with Dragons, Chapter 71, Daenerys X.
- Wikipedia: Pale horse (Bible)