The first was the plague.

Zwingli was taken sick in September and remained in a critical condition for many months.

As is so often the case, suffering and the fear of death made the claims of the other world so terribly real to him that, for the first time, he cried unto God from the depths, and consecrated his life to service of his Saviour.
[Sidenote: 1519] The second influence that decided and deepened Zwingli's life was that of Luther.

He first mentions him in 1519, and from that time forth, often.

All his works and all his acts thereafter show the impress of the Wittenberg professor.