Memes are infectious. They're ideas that want to spread. Think of them as the common cold, perhaps.
They are of the Corruption, as well as the Spiral, the Eye, and maybe also the Stranger.
Antimemes are very much not infectious: they do not want to be shared around, and will actively resist it. Maybe they could be compared to blood transfusions, that could be lethal if passed to the wrong body? I don't know. I don't have a metaphor for this.
They are, like you've said, the Spiral, the Dark, and the Stranger.
Cognitohazards are also not infectious. They're the ideas that are dangerous for you to think. They will often break your mind apart, or make you hurt others, but they will not pass on to them. They're more like a brain cancer, extremely dangerous, but not <forgot the word>
They differ a lot, and can be used by most fears, but they are mostly of the Eye, the Spiral, and the Stranger, as well as often the Slaughter due to their violent nature.
I am not entirely sure about the difference between cognitohazards and infohazards, but I'm pretty sure that infohazards are cognitohazards that can spread through text. That would make them a partially spreading dangerous disease, but still not of the Corruption.
Say that they are the same as the cognitohazards, maybe with more emphasis on the Eye.
There are memes that are cognitohazardous. Those are extremely dangerous, and often should be destroyed rather than contained. The combination of the cognitohazard entities and the meme entities, with a bigger emphasis on the Slaughter.
There are antimemes that are cognitohazardous. And to know what happens when one of those tries to force itself onto our reality, you need to read There Is No Antimemetics Division!