Researchers Discover How Cryptic Connections in Disease Transmission Influence Epidemics
This article discusses a novel technique for measuring pathogen spread in species. Specifically, recent outbreaks of white-nose syndrome have devastated the North American bat population. And while the spread of this syndrome has been partially explained by the observed social groups and dynamics of the bats, much of the spread has seemingly come out of nowhere. As one researcher puts it, “we had been seeing explosive epidemics where an entire bat population would become infected with white-nose syndrome within a month or two, and it was a mystery as to how that was happening.” So, researchers at Virginia Tech hypothesized that much of the pathogen spread could be attributed instead to so-called “cryptic connections.” Cryptic connections include things like brief, forgettable interactions and sharing airspace with others on public transportation. The researchers first studied direct social connections at bat hibernation sites, and then used fluorescent dyes to track cryptic connections between bats (along with connections between bats and other species). When white-nose syndrome eventually afflicted the studied bats, they found that their fluorescent dye model was much better at predicting its spread than the mere social networks model.
This study produced several interesting findings regarding the spread of disease among bat social networks. First, these cryptic connections explain how the disease can spread so effectively during the winter, when bats only move for brief intervals every few weeks. They found that the disease spreads easily through clusters of bats that hibernate together, and then the cryptic connections produced by the brief periods of movement are sufficient to move the disease from cluster to cluster. Second, researchers found that much of the disease spread is driven by transmission between different species. Transmission between species is hugely dependent on cryptic connections, so until now researchers had been unable to quantify just how much of an effect interspecies transmission has. However, it is now clear that a robust model of pathogen spread must fully account for inter species transmission (along with cryptic connections in general)