"U.S. Quarantine Stations are part of a comprehensive system that serves to limit the introduction and spread of contagious diseases in the United States. U.S. Quarantine Stations are located at 20 ports of entry and land-border crossings where international travelers arrive (see map). They are staffed with medical and public health officers from the Centers for Disease Control and Prevention (CDC) and managed by CDC's Division of Global Migration and Quarantine. These health officers decide whether ill persons can enter the United States and what measures should be taken to prevent the spread of contagious diseases."
Division of Global Migration and Quarantine: http://www.cdc.gov/ncpdcid/dgmq/