Red Rust

The Red Rust is an artificial virus created by the Autobot Pharma. It's spread by touch, but infected Cybertronians show no symptoms until they first transform, at which point the virus triggers and causes the coolants, dispersants and anti-rusting agents in their body to cross-contaminate and cause a molecular breakdown. The first visual sign is fuel leaking out of the victims' eyes, making it seem like they're "crying themselves to death."

Fiction

IDW comics continuity

Pharma invented Red Rust in an attempt to contaminate and shut down Delphi in order to escape a deal he had made with the Decepticon Justice Division. He paid two Decepticons, Sonic and Boom, to infiltrate the facility and detonate a "soundbomb" laced with the virus, causing everyone who heard the noise to be infected. How Ratchet Got His Hands Back Before long, almost everybody at Delphi had died, with the medics First Aid and Ambulon working overtime to hold back the infection. Five days later, Ratchet, Pipes, and Drift came to investigate and First Aid informed them of the crisis. As they proceeded with their exploration, Drift and Pipes transformed and succumbed to the the virus. Life After the Big Bang While Ratchet was also forced to transform, he figured out Pharma's traitorous plot and confronted him, acquiring his only sample of vaccine against Red Rust and using it to cure the survivors. How Ratchet Got His Hands Back