New immunization strategy better in handling epidemics, computer viruses
clusters. The algorithm could also make clusters of an arbitrary size ratio, and then divide the larger cluster again to make equal-size clusters. For example, the algorithm could divide the network into two clusters with size ratio 2:1, and then divide the larger cluster in half. When comparing the EGP strategy with different strategies, the scientists found that the new strategy exhibited advantages for immunizing all four network models tested. For instance, in the “workplace network,” which links workplaces when an employee lives in the same household with an employee from a different workplace, the EGP strategy required 15 percent fewer doses than the second best strategy (the adaptive targeted strategy). This kind of network is often used to model the spreading of influenza, as well as the spreading of information and rumors in society.
In the “autonomous system” network, which describes the Internet network and computer virus spreading, the EGP method required 50 percent fewer doses than the second best strategies (both the targeted and adaptive targeted strategies performed equally well). The EGP method had similar advantages in fragmenting a network of high energy particle physics citations (23 percent fewer doses) and a metabolic network describing the interactions between the metabolites of E. coli (20 percent fewer doses). or all networks studied, the EGP strategy minimized the infected fraction of the network population by five to ten times compared with the targeted strategy, when using the same number of immunization doses. With these advantages, the scientists hope that the new immunization strategy will benefit populations by taking a more global approach to the prevention of spreading. “EGP puts every node in consideration with its neighbors, while the targeted strategy only accounts for the individual properties of the nodes,” Chen said of the EGP’s global nature. “For an example, if you already have a network with a loosely connected large cluster and a highly connected small cluster with high degree hubs, EGP will use the rest immunization strength to make the large cluster smaller, while the targeted strategy will get rid of the hubs to make the small cluster even smaller.”
Before implementing the new strategy, the researchers plan to further evaluate its performance in various settings. “The EGP strategy is a fairly new idea, and currently it is not used in real-world situations yet,” co-author Fredrik Liljeros of Stockholm University said. “Our next step will be to evaluate the strategy in settings where a high proportion of information abort the contact patterns between individuals are known. One possible such setting could, for example, be hospitals where information about the movement of inpatients between wards is registered and stored.”
- read more in Yiping Chen, et al., “Finding a Better Immunization Strategy.” Physical Review Letters 101, 058701 (31 July 2008)
