What happened
This paper shows that when people move around and make new connections during an epidemic, the disease spreads more easily. It means that models assuming fixed social networks underestimate how fast an illness can spread.
Why it matters
Most models for how diseases spread assume that people's social networks stay the same. But in real life, people travel, meet new friends, or avoid sick ones. This paper shows that these new connections, even indirect ones, make epidemics worse. It means public health officials need to consider how human behavior changes social networks during an outbreak.