In the New Fantendoverse, it still exists within Noah with it's own district. It is mentioned during Strafe: Warzones and Leah plans to find a cure for it but got horribly sidetracked and seems to have forgotten about her plans to cure it as the story ends.
In the Mynisverse, it is not isolated to a single district, and is instead found throughout the country of Noah. The Twisted Cross has recently developed a cure, but is asking for a very high price for it; and even then, it doesn't always work properly.
The Rot causes the host's body to slowly decay over time, reducing their life expectancy by a large time. A host of the Rot can be identified by their pale grey skin colour, hair loss, and a lack of fingernails or toenails.
In the latest stages, the host's nose, ears, fingers and toes are likely to simply fall off before they die a short time afterwards. Some hosts in the Mynisverse, like Strafe, have even lost whole limbs to the final stages of the disease.