Every year, an influenza epidemic hits the United States.
On average the disease takes about five weeks to spread across the country, but there is considerable year-to-year variation: from 2 to 8 weeks.
CIDD researchers Bryan Grenfell and Ottar Bjørnstad, together with colleagues at the National Institutes of Health, have identified some interesting patterns in the U.S. 'flu epidemic data:
- Epidemics caused by Influenza A H3N2 virus are more severe and more spatially synchronized than those caused by Influenza A H1N1 and Influenza B viruses.
- If an epidemic begins in a state with a large population (such as California), it spreads more quickly and widely than if it starts in a less populated state (such as Wyoming).
- The timing and amplitude of epidemics is correlated with patterns of movement to and from workplaces, rather than being a simple function of geographical distance. This suggests that the regional spread of influenza is primarily governed by the movement of adults rather than children (although local spread may be affected by movement of children).
In a paper in Science, the researchers discuss how these results affect predictions about the spread of annual influenza epidemics, as well as pandemic influenza.
Written By: Cн©cile Viboud, Ottar N. Bjнџrnstad, David L. Smith, Lone Simonsen, Mark A. Miller, & Bryan T. Grenfell
Journal: 312: 447-451
Journal Reference: 312: 447-451
Paper Id: 10.1126/science.1125237