Swine Flu Simulation Predicts 1,700 Cases By June

Professor's Computer Simulations Show Worst-Case Swine Flu Scenario from Northwestern News on Vimeo.

By Frank James

How many swine flu cases will the U.S. have in the next four weeks?

No one really knows. But computer modeling permits an educated guess and that's where a group of Northwestern University researchers comes in. Based on computer simulations they've run, under a worst-case scenario in which authorities do very little to intervene, we reach 1,700 victims in four weeks.

Here's how a Northwestern press release explains it:

Associate Professor Dirk Brockmann (http://rocs.northwestern.edu/) and his research group have found that the major areas projected to have incidents in the worst-case scenario include California, Texas and Florida. Worst-case scenario means that no measures have been taken to combat the spread of disease. These numbers would, of course, be lessened by preventive measures already under way.

Under the worst-case scenario, more than 100 cases are projected for the Chicago area. The affected locations largely correspond to major transportation hubs in the country. The researchers also will be running simulations on the possible time course of the spread of swine flu in Europe.

Brockmann says their swine flu results are in excellent agreement to those of a research group at Indiana University led by Alex Vespignani that is using a different method.

"The Indiana group uses a different computational approach, and the agreement of our results is promising and an indicator of reliability in both methods," says Brockmann, associate professor of engineering sciences and applied mathematics at the McCormick School of Engineering and Applied Science (http://www.mccormick.northwestern.edu/).

Brockmann and his doctoral students Christian Thiemann, Rafael Brune and Alejandro Morales-Gallardo are constantly updating the simulation, taking into account new information on confirmed cases and more precise information on transmissibility and disease-specific parameters.

Brockmann has extensive experience modeling the spread of disease. His high-performance computer clusters can be used to simulate an infectious disease that spreads among 300 million people.

"We can, on a very realistic scale, try to model an epidemic that has the same size as a real epidemic," he says. In order to understand how disease travels, Brockmann also must understand human transportation networks.

Of course, the number of actual cases should be less than the Brockmann team's worst-case scenario since measures, including some fairly aggressive ones like school closings and even some mandatory isolation of suspected cases, are occurring in various jurisdictions.

Even if the Brockmann team's worst-case scenario materializes, the nation's healthcare system should be able to cope with that level of new cases though there could conceivably be local problems in places with not enough health providers.

That means we should reach the summer, when the swine flu virus like other influenza viruses, is expected to go to ground without straining available healthcare resources.

The big and worrisome question, which Brockmann likely can't simulate very well since there are too many unknowns, is what happens next fall when flu viruses always make their return in the northern hemisphere, especially after this H1N1 virus has once again reassembled its genetic material, adding new genetic information from other viruses?