Inuko

This SCP is a memetic disease that's spread through social interaction, specifically any kind of face-to-face interaction (basically a phone call or passing notes won't get you infected, but a Skype session or direct conversation will). The disease initially makes people more upbeat and sociable (this is a latency period where infectees are still curable), but over time they grow massive smiles that make them unable to eat/drink. 95% of infectees die of thirst/starvation, while the surviving 5% are able to subsist on social interaction and project speech telepathically. The only people who are immune to the disease are individuals with prosopagnosia, a disorder that leaves people unable to recognize faces.
To contain it, the Foundation maintains an AI that looks for signs of people infected with this SCP and runs it by a team of analysts with prosopagnosia. Then, if confirmed, the Foundation sends in an MTF to isolate the infection zone, tranquilize everyone, single out the incurably infected for elimination, then quarantine the survivors and involved personnel. If anyone advances to the terminal infection stage, they are eliminated, otherwise they're amnesticized and released.
An addendum would include a journal written by a prosopagnosaic survivor of this outbreak, who provides the initial MTF an understanding of how to contain it. This survivor watches the disease devour her friends, family, and neighbors while she tries in vain to save them, before retreating out of town and possibly killing herself.
The last addendum would include an interview with an Infectious Smile infectee, who explains that he can't comprehend the negative effects of what he's transmitting and that all he wants is to spread happiness and togetherness to everyone.

Any feedback is greatly appreciated. Let me know if this is too hard to contain, or if the procedures are too extreme. I have a full draft ready if needed.