Because flu viruses mutate nearly once every reproduction cycle, no two people are made sick by precisely the same virus, as illustrated by this chart documenting swine flu cases among humans in early 2009.

The recent outbreak and sudden spread of a novel H1N1 influenza virus has caused a worldwide concern and has tested our ability to respond to major public health challenges. Significant scientific resources have been marshaled to discover the best possible responses against this novel swine origin influenza virus. A group led by Raul Rabadan at the Center for Computational Biology and Bioinformatics, and the Department of Biomedical Informatics at Columbia University has been studying the evolution of influenza viruses and the origins of flu pandemics by analyzing large data sets that contain genomic information.

After the first news of the outbreak in April 2009, the group worked intensely to decipher the origins, the diversification, and the spread of the pandemic virus, and investigated the factors that could contribute to its virulence. The results of these studies are published in major scientific journals including the New England Journal of Medicine, Eurosurveillance, PLoS, etc., and have received special attention from the media, including: 

- CNN
- Reuters International
- Associated Press and ABC News
- China Radio International

The Rabadan lab was also the subject of the cover story in the Fall 2009 issue of the Columbia Magazine.

Portion of this work was performed in close collaboration with Gustavo Palacios and Ian Lipkin at Columbia University and the researchers at the Institute for Advanced Study in Princeton, New Jersey.