Stewart Simonson was the first Assistant Secretary for Public Health Emergency Preparedness at the U.S. Department of Health and Human Services (HHS). He assumed office on April 28, 2004. He told the president in a resignation letter dated May 13, 2006 that he had accomplished what he had set out to do, and it was time to pursue other opportunities. Simonson joined HHS in August 2001 and was instrumental in building the HHS preparedness and response organization that grew out of the September 11th attacks. He currently serves as the Assistant Director-General of the WHO at the United Nations.