Understanding networks helps control epidemics

Understanding the structure of global trade and transportation networks can be a major tool for effectively combatting the spread of pests and diseases, according to a new study by a team of Plant Biosecurity CRC researchers from CSIRO and Murdoch University.

Source: Plant Biosecurity CRC

Globalisation has meant that these networks are more complex and pervasive than ever before and it is increasingly easy for pests and diseases to spread around the world, as highlighted by the CSIRO Australia’s Biosecurity Future report last year.

“A good understanding of the way global trade and transportation networks work really helps understand how pests and diseases spread,” says Natalie Banks, the paper’s lead author.

“This study found that some of the fundamental aspects of network structural patterns have the potential to dramatically increase the speed and size of epidemics and pest invasions.”

Network patterns reviewed in the paper include Scale-free Networks, where the majority of towns, cities or ports have only a few links to other nodes but several are hubs with many links, such as the Worldwide Airline Network (WAN). This is how SARS was able to spread to 37 countries via the WAN hub of Hong Kong, infecting over 8,000 people within a matter of weeks.

Small-world Networks have similar numbers of links to and from each node and can be highly clustered. These clusters can be very densely connected internally but less well-connected to each other, such as the Global Road Network. An example is the current Ebola outbreak, which has spread widely within the well-connected West African region but less successfully to other parts of the network.

“Understanding the nature of these patterns, as well as the ways global networks are connected to each other and the roles particular nodes or links play in network connectivity, can help pinpoint the areas in networks that are the most vulnerable to infections and invasions, and those with the greatest spread potential,” said Ms Banks.

“We can then target our limited resources at the points where they will be the most effective, saving critical time as well as resources. We will be in a much better position to more effectively control epidemics during their initial stages, when both impacts and costs are low.

“Network analysis can be a highly useful tool for improving the ways we deal with emerging pests and pathogens.”

Article reference: The role of global trade and transport network topology in the human-mediated dispersal of alien species” is published in the February 2015 issue of Ecology Letters, DOI: 10.1111/ele.12397

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