Virgil's Contagion

Your touch inflicts disease. Make a melee spell attack against a creature within your reach. On a hit, the target is poisoned.

At the end of each of the poisoned target’s turns, the target must make a Constitution saving throw. If the target succeeds on three of these saves, it is no longer poisoned, and is inflicted with flesh rot. If the target fails three of these saves, the target is no longer poisoned, but choose a disease or infection. The target is subjected to the chosen disease or infection for the spell’s duration.