Talk to each villager and get them to describe their symptoms before curing them with a Cure Common Disease effect - either a spell or a potion will do. Once all three are cured, return to Ratagos.
The symptoms they describe are tiredness and a pain in the neck, which Ratagos identifies as the symptoms of Porphyric Hemophilia - the vampire disease! Your reward for curing the villagers is the Staff of Meris' Grace and five Temple reputation points.
If you don't cure the villagers within three days, they turn into vampires and you will be forced to kill them. In this case, you receive two scrolls rather than the staff.
The following Journal ID and Index codes can be used with the Journalconsole command to manually update the quest to a certain point.
Epidemic in Ranyon-ruhn (TR_m1_TT_5)
Index
Finishes Quest
Journal Entry
10
Ratagos wants me to heal three residents of Ranyon-ruhn who have been stricken with some spreading epidemic disease. The three in question are Verana and Arthal Eindari, both of whom live in Arthal's house, and Dilnar Llenim.
20
I arrived too late, and the one of the victims of the mysterious disease had become a vampire.
30
Finishes quest
Ratagos thanked me for ending the epidemic in Ranyon-ruhn, and lamented that Porphyric Hemophilia had been allowed to spread to Ranyon-Ruhn.