In the late 1990s, there was growing recognition of factors that had increased the risk of infectious disease in the prior decades, including high-volume international travel, global urbanization and population growth, increased interaction between humans and wildlife, antimicrobial resistance, and bioterrorism concerns. In 2000, domestic interstate quarantine authority for humans was transferred from the Food and Drug Administration (FDA) to CDC, which FDA had had since the late 1960s, although FDA still retained domestic interstate quarantine authority over animals and other products. After the 2002–2004 SARS outbreak, CDC reorganized the system, creating the Division of Global Migration and Quarantine and expanding to 20 stations.
