Exodus 32:35:

And the LORD plagued the people, because they made the calf, which Aaron made.

Notes on Exodus 32:35:

This is one of many verses that describes sickness as a curse for sinning.  You have been redeemed as a Christian, so there is no valid reason for you to have to endure sickness of any kind.

See also:

Sickness as Chastening and Judgment in the Old Testament