For a prominent Darakhul see Annelies Zandstra, harbormaster and regent.
Concentration
The Beginning
Amber Fever killed millions, leading to a quick, coughing death by the next morning. The victim would rise as a mushroom encrusted zombie and murder those around it, continuing the spread. With an expensive dose of Seregon given in time, the victim would fully recover. If Seregon was given, but not in time, the victim would turn into a sentient ghoul, fully intact with their faculties. They would forever require a regular dose of Seregon to avoid turning feral. Thus a new species was born, the Darakhul.
Desperation in Seregon
To have enough money to buy Seregon in an emergency for a family of four, would require six months of saved wages. About a quarter of people in the US can afford that, so you can figure that holds true in this city.
This can lead to some desperate actions. You will absolutely steal, beg, prostitute yourself, or get involved in unsavory business to save your family. The alternative is leaving a coughing loved one on the street at night. What Sovereign Morel does with them is a mystery, but they aren't seen again. This desperation makes Seregon particularly dangerous.
It's not surprising that many people owe money or favors to those in power. Churches will often provide Seregon to especially devout parishioners in need, leading some to become militantly religious. Certain employers, guilds, and crime organizations will also promise medicine to their star people.
There are enough unsavory choices that there's almost always a way to prevent someone from succumbing to the illness. The Walraven Consortium is happy with this status quo.
As for darakhul's, they are a serious burden on families. They require monthly doses of Seregon (50gp), eat prodigious amounts of (expensive) raw meat, and they don't generally get along with others. Many don't integrate well with their families, despite the sacrifices to save them.