Summer admits that August's face does take some time to get used to. However, she doesn't feel bad for him anymore; she keeps sitting with him because he's fun and nice. Summer is annoyed that a lot of kids are acting too grown up to play. They're all interested in "hanging out" and only talk about who's cute and who likes who. August still likes to play foursquare.
While playing foursquare one day, Summer learns about the Plague. Supposedly, anyone who touches August has thirty seconds to wash their hands before they catch the Plague. Nobody has touched August because of this. Summer only finds out because Maya confides that she won't play foursquare because of it. Maya agrees that it's a stupid reason, but insists on avoiding August anyway.
Remember that Jack and Julian shook August's hand when they showed him around school the first time. When comparing that moment to this one, Maya's agreement that the Plague is stupid shows that this sort of exclusionary action can only function in a larger group when all members of the group buy into it.