1. Department of Computer Science, University of Colorado, Boulder, CO 80309, USA.
2. BioFrontiers Institute, University of Colorado, Boulder, CO 80303, USA.
3. Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA.
4. Ewing Marion Kauffman Foundation, Kansas City, MO 64110, USA.
5. Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA.
6. Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, MA 02115, USA.