The blood flux is evidently dysentery. Are there other ASOIAF diseases that are real diseases under other names?

The Great Spring Sickness is a parallel for the Black Death (bubonic plague).

Butterfly fever sounds like a cross between Kuru and Ebola.

Shaking sickness is epilepsy.

Grey plague/greyscale is a weird combination of the Black Death and leprosy. 

Redspots is chickenpox.

The pox is, well, syphilis.