The Bio Bomb is an upgrade for the GLA Bomb truck. It makes detonation of the truck even more lethal toward infantry as it will poison anyone who goes near the poison clouds after the bomb truck is destroyed. Due to it using Anthrax, it benefits from the upgrades the GLA developed for it (Namely, Anthrax Beta and Anthrax Gamma). As the detonation of one of bomb truck with this upgrade leaves a toxic residue for a brief time, it can be used effectively to counter infantry and lighter vehicles, although the effect is negligible on heavy vehicles and structures.
Even with this upgrade the bomb truck was still just as vulnerable to Aircraft and long range attacks.