Who has the authority to enforce isolation and quarantine because of a communicable disease?.
The Federal government derives its authority for isolation and quarantine from the Commerce Clause of the U.S. Constitution. Under section 361 of the Public Health Service Act (42 U.S. Code § 264), the U.S. Secretary of Health and Human Services is authorized to take measures to prevent the entry and spread of communicable diseases from foreign countries into the United States and between states.
The authority for carrying out these functions on a daily basis has been delegated to the Centers for Disease Control and Prevention (CDC).
Under 42 Code of Federal Regulations parts 70 and 71, CDC is authorized to detain, medically examine, and release persons arriving into the and traveling between states who are suspected of carrying these communicable diseases. As part of its federal authority, CDC routinely monitors persons arriving at land border crossings and passengers and crew arriving at U.S. ports of entry for signs or symptoms of communicable diseases.
When alerted about an ill passenger or crew member by the pilot of a plane or captain of a ship, CDC may detain passengers and crew as necessary to investigate whether the cause of the illness on board is a communicable disease.
Does the US President have the power to quarantine a state or other locality?
The president's power to order a quarantine is indirect, through the US Constitution Article II, Section 3, "shall take Care that the Laws be faithfully executed". The president has the power to order the U.S. Secretary of Health and Human Services to impose a quarantine by using the authority granted to the Secretary by the Congress.
Has this action ever been taken or attempted before?
See, brief History of Quarantine from the CDC.
For a more detailed history, see, Origins of Federal Quarantine and Inspection Laws.
This document mentions three cases where the federal government through the Marine Health Service (MHS) (a forerunner of the CDC) implemented local quarantines. These were done after "An act granting additional quarantine powers and imposing additional duties upon the Marine-Hospital Service" (1893), but before the current authority under the Public Health Service Act (1944).
One of the first successes to result from this power came in response to a smallpox outbreak in Eagle Pass, Texas, in July of 1895. The victims of the epidemic were a group of 300 African-American agricultural workers from Alabama and Georgia who had contracted smallpox in Mexico, where they had been lured by the false promise of owning land. The people of Eagle Pass responded to this group with hostility and avoidance, due to past experiences with epidemics introduced by migrating agricultural workers. State efforts to deal with the outbreak were inadequate; no one created a registry of the infected and there was no organized effort to separate the sick from the well. As some of the victims began to die, the lack of state control allowed the infected men to leave the area out of fear that they would meet the same fate. Once the situation became known to federal officials, Surgeon General Wyman assumed control of the situation by appointing Dr. Rosenau, a MHS officer, and employing twenty guards to organize separate camps for the sick men and the apparently well men. After this action was taken, no additional cases of smallpox occurred, and two-thirds of the 178 men who had already been infected survived the epidemic.
On March 6, 1900, the body of a Chinese immigrant was found dead in San Francisco's Chinatown. The San Francisco Board of Health determined that the unfortunate man had died of plague and instituted a quarantine of an area the size of twelve city blocks. The diagnosis of plague was rejected, however, by city officials, and the Board of Health sought support in its diagnosis from the Marine Hospital Service. Dr. Joseph Kinyoun came to San Francisco to examine the body, and determined that the disease proved bacteriologically to be bubonic plague. Following this confirmation, the MHS carried out quarantine measures in San Francisco from March until June of 1900, including disinfection and fumigation of ships at the city's harbor and inspection of trains at its borders. Despite the confirmed diagnosis, however, the people of San Francisco strenuously protested the quarantine. Even the Governor of California denied the presence of plague, and by June of 1900 state opposition led to an end of federal involvement for over six months. Indeed, almost every newspaper in the city vilified the City Board of Health, Dr. Kinyoun, and San Francisco's mayor for implementing the quarantine, one terming them the "perpetrators of the greatest crime that has ever been committed against the city".
Though it is easy to understand why one might resist believing that one's city was infested with plague, it is more difficult to understand why the protestors might have thought the Board of Health and MHS would fabricate the disease. The roughly 20,000 Chinese-American residents of San Francisco clearly thought the quarantine was motivated by the anti-Chinese sentiment present in the city at the time. In addition to this group, however, the business community in and near Chinatown also objected to the quarantine and diagnosis of plague on the grounds that it was bad for business. This mistrust of health officers seriously hampered their efforts to prevent the spread of plague for the rest of the year, resulting in 122 deaths. Attempting to prove to San Franciscans that the presence of plague was real, the Surgeon General assembled a special commission of prestigious university medical professors to investigate. Their findings, combined with the increasingly undeniable reports of deaths from the disease, finally convinced all local physicians and enabled city and federal health officers to take more effective action. A year after plague was first discovered in San Francisco, the Governor of California, under pressure from state health officers and neighboring states, finally requested that the federal government re-initiate comprehensive fumigation and sterilization programs.
The lesson of the plague of 1900 had been well-learned by the time of the next outbreak in San Francisco. After the great earthquake of 1906, the upheaval of buildings led rats to scatter out into the city, carrying plague with them. In the years since the last epidemic, the scientific community had concluded that rats themselves were the source of the problem, and that human-to-human transfer of the disease was unlikely. Because of this discovery, public health officials' first response to the disease was to quarantine rats, rather than people, and to conduct extensive sanitation and disinfection programs throughout the city. This time, the people of San Francisco welcomed federal health officers into the city, and admitted the presence of the disease when it was diagnosed. The federal health officer assigned to direct the disease-control efforts, Dr. Rupert Blue, became an icon rather than a villain: "The name of Dr. Rupert Blue came to be a household word that was regarded almost with reverence." Six months after the start of the 1907 outbreak, it ended in a celebration among San Franciscans, their city health officers, and the federal health officers involved, including a banquet held in the main streets of the city "to emphasize that San Francisco was now so clean that one could eat a meal in the street."