Mark 1:30

But Simon's wife's mother lay sick of a fever, and anon they tell him of her.

But Simon's wife's mother lay sick of a fever. Luke as was natural in "the beloved physician" (Colossians 4:14), describes it professionally; calling it a "great fever" [ puretoo (G4446) megaloo (G3173)], and thus distinguishing it from that lighter kind which the Greek physicians were wont to call "small fevers," as Galen, quoted by Wetstein, tells us.

And anon - or 'immediately' they tell him of her-naturally hoping that His compassion and power toward one of His own disciples would not be less signally displayed than toward the demonized stranger in the synagogue.