27, the blood painting: While the individuals were not confirmed as affected, the incident gave signs that those who had witnessed the SCP were capable of spreading it themselves, rather than that only being possible by the tapes and derivatives thereof. This, if true, would be a huge thing, and would have to be treated with utmost caution.
33, the not-blood painting: While there was not evidence of it being infectious when created, again, caution was exercised when it was collected; they were planning experiments with it to confirm it being an instance of 1792, but then the next even happened.
34, the security system: When the guard on duty witnessed 33 on the camera, he knew that 33 was an instance of the SCP; he had definitely saw the painting clearly, and yet he could not properly describe what it was. Now, earlier in the article, it states that, for example, a tape inserted into a VCR and then removed without playing it would still infect the VCR, meaning that it spreading was immediate. The SCP was recorded on the security system now; they had not yet determined how it interacted with computers at that point, so the possibility that everything on it was contaminated was high. Attempting to check it carried a huge risk that it would infect the person using it; as they had just confirmed that the SCP can infect humans as well as digital media, this was something they could not risk.
I am working on rewriting some of these sections to be a bit clearer, and to fix some inconsistencies found in them, but hopefully this clears up what you were wondering here.