The Site-17 Outbreak was a horrific tragedy that occured inside of the S.H.I.E.L.D. helicarrier, and was the first sighting of the necromorph plague on Earth.
S.H.I.E.L.D. scientists had discovered a mysterious artifact deep within the arctic, during the same expedition that discovered Steve Rogers. The artifact was discovered when a surge of radiation was found inside of what looked to be a crashed escape pod buried in snow. The pod was transported back to the helicarrier for research, and was opened by several robots in case of casualties. As the mechanical can openers weren't trained for combat, a necromorph inside of the pod had escaped undetected.
After several hours of pointless studying in the Site-17 sector of the research level, the Marker had been locked away in storage, though several scientists later showed subtle signs of dementia. While the artifact was being escorted by security, the team had been attacked by a strange flying creature. Unable to subdue it in time, it successfully killed the three men and "infected them", turning them into creatures similar to itself. The four necromorphs roamed the research level of the Helicarrier, until they had reached a populated area that was studying a frozen corpse found crushed under the pod. Security managed to evacuate at least a hundred personnel when it attacked several scientists, though they managed to slaughter many of the research and security team. A team of engineers repairing minor damages to the ship's core had been alerted from the screams and gunfire from the event over security cameras, and helped security evacuate civilians by radio. They had managed to help a team of eleven guards and seventeen scientists escape to a safe, underground safehouse.
An emergency had been declared after a last surviving security officer activated a red button under a table that looked useful. A team of eleven men entered the research level, and found that the entire level had been overrun since the distress signal was detected, and that it had spread to the barracks. After losing several men, Nick Fury ordered that both areas were incinerated in order to prevent an epidemic, should the creatures cause the ship to go down, or a carrier-level outbreak. After discovering that there were still movement in the barracks and research level, they were both jettisoned into Shrek's swamp.
Shrek had written a complaint of receiving a gift of a bunch of alien zombies and a family of terrified scientists and guards. The event was covered up by both the SCP Foundation and S.H.I.E.L.D., and the official story for the deaths of the staff was a terrible fire that occurred after a soup can exploded. S.H.I.E.L.D. sent eleven more research parties back into the Arctic, to find and destroy any other "Markers" that could have been present. However, none were found. The Foundation had ceased any downloaded or remaining research of the Marker, and sent a written request to Shrek to return the artifact from storage. The ogre had crushed it up and ate it like rock candy hours before the message was received, however.