SWINE FLU SPREADS MOSTLY THROUGH FRIEND NETWORKS. “A new study of a 2009 epidemic at a school in Pennsylvania has found that children most likely did not catch it by sitting near an infected classmate, and that adults who got sick were probably not infected by their own children. Closing the school after the epidemic was under way did little to slow the rate of transmission, the study found, and the most common way the disease spread was a through child’s network of friends.”