SUMMARY
Decades ago, a multi-factor perspective offered valuable insights into the causes of population cycles in arvicoline (= microtine) rodents. Multi-factor perspectives are also critical for understanding the ecology of infectious diseases. Here, we provide examples of how these perspectives inform our ability to predict variation in disease risk through space and time. We focus in particular on the evidence that many emerging zoonotic pathogens of humans have multiple hosts rather than just one, that most host species harbor more than one pathogen and that these pathogens interact, and that understanding variation in the abundance of species that transmit pathogens often requires deep exploration of the ecological community in which those hosts are embedded.