Why did they attack us? —Ahsoka Tano after clones attack her and Barriss
A skirmish on board the TK-73 was between infected and uninfected clone troopers and Jedi in a Alternate Universe. Later during the battle all the clones and jedi were infected by the Brain Worm then docking with a medical station, which started the Worm Wars.
After the Second Battle of Geonosis a clone trooper squad was sent to check out the remains of the Progate Temple. While in the catacombs of the temple the clone troopers didn't find the body of the queen, so they rushed back up to tell Anakin Skywalker while on their way back up the clone in the back of the group was infected by a Brain Worm. When they got back up to the surface the clone that was infected was assigned with some of Tango Company and Two Jedi Knights on a mission to deliver medical supplies to a medical frigate.
Don't worry, this won't hurt —A clone trooper before infecting Ahsoka
Going to the clone barracks with brain worm eggs CT-3291 walked in and placed the eggs and they hatched crawling into the clones noses and taking control of their brain and making them pass out. When they woke up they went to the pilots corridors after they went into hyperspace and infected them too put more under the worm's control. When Ahsoka and Barriss went to eat they were attacked by two clones who they killed as a last resort, when two more clones entered and also opened fire they pushed them into the wall knocking them out. Deciding to split up Barriss took the communications and Ahsoka the cockpit, when Barriss entered the communications room she tried to call for help but got no answer. After trying for ten minutes to contact for help Barriss was forced to fight three infected clones she managed to knock two out and almost kill another one but after she stabbed him the brain worm in his body slithered on to her and crawled up her nose. and While walking to the cockpit for a hour Ahsoka ran into Barriss who lied that she contacted for help and that they were coming, but then Ahsoka realized that Barriss wasn't acting herself but then Barriss started engaging her in a lightsaber battle. After fighting for five minutes in the cockpit and down a hallway Ahsoka was just about to cut the brain worm out but not before the infected clones pinned her to the wall and then waited for barriss to infect her. Trying to get out Ahsoka was able to punch one of the guards but to no effect another clone pinned her arm, as Barriss approached Ahsoka begged her to not do it but Barriss eventually got close enough so that the brain worm could crawl up her nose and infect her.