Catriona plague

In Game
"A disease which quickly spread through all the northern countries after the war with Nilfgaard. Those who suffer from catriona die a terrible death - their convulsions become stronger each day, they vomit blood and mucus, and have bloody diarrhea. After a fortnight or so they die in agony."

St. Lebioda's Hospital in the Temple Quarter of Vizima is filled with the victims of catriona, and Shani spends her time trying to help them in Chapter II and Chapter III (and, supposedly, in Chapter IV).