From Halopedia, the Halo wiki
Following a terrorist attack on the Outer Colony of Sedra on February 7, 2556, Noah entered into correspondence with Ader Haddak, a member of Sedra Emergency Response Unit 54. The two individuals exchanged numerous videos with one another wherein they discussed the weapon used in the incident and its dispersal method. Ader sent Noah all the data from the event that he could and in return, Noah shared his analysis. He concurred that the agent was a previously-unrecognized element and pressed Ader to continue studying it. Unfortunately, doing so was quite difficult, owing to the element's short half-life. Ader told him one sample of infected tissue had been preserved in Sedra City in cryostasis that offered the best chance at research. At one point in the conversation, Noah discussed the pathophysiology of the element's toxicity: it prevents lymphocyte mitosis cells from dividing, which hampers the immune response and leads to rapid further destruction throughout the body. Eventually, Noah also began to note that the means of dispersal used to infect the population of Sedra City was remarkably similar to that used by the Halo Array, insofar as a field was radiated outwards that only affected specific forms of carbon-based life. He was terrified at the prospect of a Covenant faction reverse-engineering part of the Halos' technology. At this point, ONI's transmission software recognized a breach of contact and due to the highly sensitive nature of the intelligence Noah was sharing. He was cut off in the middle of recording a video response to Ader and their interaction was flagged, encrypted, and sent to Codename: FIXER.
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