quarantine was shifted to the Centers for Disease Control (CDC). For several years following that shift, CDC's Foreign Quarantine Division (currently the Division of Quarantine) operated 55 domestic quarantine stations and had a sizable presence abroad. Since then, this number has been greatly reduced, in line with modern epidemiological concepts and technologies. Last year, 7 domestic stations remained open, and in early 1992, the San Juan, Puerto Rico, station was reopened with a staff of one (C. McCance, Director, Division of Quarantine, Centers for Disease Control, personal communication, 1992).

Currently, the United States does not require immunizations for entry within its borders. The master of a ship or commander of an aircraft, however, must radio immediately to the quarantine station at or nearest the port of arrival to report any death or illness among passengers or crew. This procedure allows for the arriving carrier to be handled in a controlled manner. To supplement the few remaining quarantine stations, U.S. Immigration and Naturalization Service and U.S. Customs Service inspectors have been trained to inspect all passengers and crew for signs and symptoms of communicable diseases at ports to which CDC staff have been assigned. Persons who are suspected of being ill are referred to them; if the port has no such personnel, CDC staff at the nearest quarantine station are called. The agency has contract physicians at all ports of entry for medical backup. Certain animals, shipments of etiologic agents, and vectors of human diseases are required to have import permits, and their mode of shipment must conform to requirements.

Prior to 1985, CDC listed 26 diseases that invoked its authority to detain, isolate, or provisionally release persons at U.S. ports of entry. Today, only 7 such diseases are listed: yellow fever, cholera, diphtheria, infectious tuberculosis, plague, suspected smallpox, and viral hemorrhagic fevers. Over the past decade, this authority has been used only three times (C. McCance, Director, Division of Quarantine, Centers for Disease Control, personal communication, 1992).

Smallpox

The most heartening evidence of humankind's ability to triumph over infectious diseases is the eradication of smallpox. A systemic viral disease characterized by fever and the appearance of skin lesions, smallpox is believed by some to have been responsible for the death of more people than any other acute infectious disease. It has also been one of the most feared of all contagious diseases.

Like plague, smallpox was an ancient affliction. There is good reason to think that the Egyptian pharaoh Ramses V died of the disease in the mid-twelfth century B.C. (Fenner et al., 1988; Behbehani, 1991). A disease



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