The period of isolation decreed to control the spread of disease. Before the era of antibiotics, quarantine was one of the few available means of halting the spread of infectious disease. It is still employed today as needed. The list of quarantinable diseases in the U. S. Is established by Executive Order of the President, on recommendation of the Secretary of the Department of Health and Human Services, and includes cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, and viral hemorrhagic fevers (such as Marburg, Ebola, and Congo-Crimean disease). In 2003, SARS (severe acute respiratory syndrome) was added as a quarantinable disease. In 2005 another disease was added to the list, influenza caused by novel or reemergent influenza viruses that are causing, or have the potential to cause, a pandemic.