The Tiberium infusion is a superior method of human augmentation that entered combat service within the Brotherhood of Nod during the Third Tiberium War. With roots in the ReGenesis project and the Divination technology, the infusion is a safe and cheap method of augmenting humans, specifically militia and fanatics, who receive it at Secret Shrines.
The infusion augments the receiver's perception, speed and endurance as well as making them completely immune to harmful effects of Tiberium. The Black Hand refuses to practice Tiberium augmentation, and as such, doesn't allow their troops to undergo infusion.
However, one of the added effects of Tiberium augmentation is that they become more vunerable to weapons they wouldn't normally be effected by. For example, a Nod Millitant squad with the tiberium infusion upgrade can be destroyed by the catalyst missile.
Encounters with the Scrin Reaper-17 sect have shown that excessive infusion causes mutations and mental instability, even within a race that thrives on Tiberium. It is unknown if humans infused with Tiberium can also suffer from these effects.