Simulation of a pandemic flu outbreak in the continental United States, initially introduced by the arrival of 10 infected individuals in Los Angeles.
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The spatiotemporal dynamics of the prevalence (number of symptomatic cases at any point in time), is shown on a logarithmic color scale, from 50 or fewer (green) to 100 or more (red) cases per 1,000 persons. Without vaccination, antiviral drugs, or other mitigation strategies, the entire nation becomes infected within a few months. Depending on the reproductive number R0, effective intervention strategies including vaccination and targeted antiviral prophylaxis can be successful without resorting to economically damaging measures like school closure, quarantine, and work or travel restrictions. This large-scale agent-based simulation involves 280 million people, and uses demographic and worker flow data at the Census tract level, as well as long-range travel statistics, to describe the geographic movement of people. In this simulation, long-range travel is assumed to occur at a lower-than-normal rate (10 percent) due to travel advisories, but with no other mitigation strategies the pandemic quickly spreads nationwide, peaking about 90 days after the initial introduction.

Green: 50 per 1,000

Red: 100 or more cases per 1,000 persons
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The pandemic simulation model was implemented in the Laboratory's celebrated Scalable Parallel Short-range Molecular dynamics (SPaSM) large-scale simulation platform developed for the nuclear weapons program. It runs on the Los Alamos supercomputer known as Pink, a 1,024-node (2,048 processor) LinuxBIOS/BProc Science Appliance running Clustermatic 3, the largest single-system image Linux cluster in the world. Pink's nodes have dual 2.4 GHz Intel Xeon processors (Pentium 4) with 2 gigabytes of memory per node. The purchase of the Science Appliance was funded by the National Nuclear Security Administration's Advanced Simulation and Computing program. Pink is currently a system software research platform, a science appliance cluster concept invented at Los Alamos in the Computer and Computational Science Division.

[Imagery courtesy of Timothy C. Germann, Kai Kadau, Catherine A. Macken (Los Alamos National Laboratory); Ira M. Longini Jr. (Emory University)]

The full paper, by a team of scientists from Los Alamos National Laboratory in New Mexico, the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle, was presented in the Proceedings of the National Academy of Science April 11, 2006. See the Los Alamos National Laboratory press release at http://www.lanl.gov/news/index.php/fuseaction/home.story/...

The text of the National Institute of General Medical Sciences press release can be accessed at http://www.nigms.nih.gov/News/Results/FluModel040306 .

For more about Los Alamos National Laboratory, see http://www.lanl.gov online. (less info)