However, nodes with fewer connections but locations near the core, i.e. high k-shell values, were just as likely to spread information or infections as similarly situated nodes with more connections. Hence, they conclude the most efficient spreaders are located in a network's inner core.
"In the case of LiveJournal, someone with a thousand friends but a low k-shell level will have less impact than someone with a hundred friends but a high k-shell level," Professor Makse said. "Small players and big players spread just as well if they are at the core of the network.
For the spread of disease, nodes located in high k-shell layers are more likely to be infected and they will be infected sooner than other nodes, the researchers found. "The neighborhood of these nodes makes them more efficient in sustaining an infection in early stages, thus enabling the epidemic to reach a critical mass such that it can fully develop."
This knowledge could greatly help public health officials trying to head off an epidemic in situations where limited quantities of vaccines are available, Professor Makse said. "You try to identify the most likely spreaders and vaccinate them first."
The researchers explained the existence of hubs at the periphery of real networks as a consequence of their "rich topological structure. In a fully random network, all hubs would exist near or at the core and they would contribute equally well to spreading.
While high k-shell value nodes were found to be the best single spreaders, regardless of their connectivity, this did not necessarily hold up for situations involving multiple spreaders. In those cases, connectivity between hubs did not accelerate the spreading because of the overlap of infected areas created by the different spreaders.
"The better spread
|Contact: Ellis Simon|
City College of New York