Given these uncertainties, important information and insights can come from generating a potentially dangerous virus in the laboratory. While the World Health Organization and the Centers for Disease Control (CDC) and Prevention provide excellent public health surveillance for novel influenza strains, influenza outbreaks still occur suddenly and in unexpected places. The recent H1N1 pandemic exemplifies the problem: In 2009, a new influenza virus emerged. It was shown to have originated from an animal reservoir, and it spread so rapidly that it strained the pharmaceutical industry’s capacity to prepare vaccines fast enough to blunt its spread. We do not fully understand the underlying factors that allow influenza viruses to be transmitted efficiently in humans after they emerge from different species. The ferret transmission studies were intended in part to fill these important gaps in knowledge.