Leviticus, the third book of the Bible, provided the ancient Hebrews with an instructional manual during their years of wandering. Some of these guidelines pertained to ways of maintaining the health and integrity of this nomadic community: proscribed foods, distinctions between clean and unclean things and preventive health measures.
In Chapter 13 comes a statement concerning individuals with certain diseases (called tsara’at, a complex of ailments loosely translated as leprosy). “Being unclean he shall dwell apart; his dwelling shall be outside the camp.” The indicted person, when eventually found free of disease, was then allowed to return.
To understand this uncompromising action, four assumptions are made: First, these nomadic Hebrews believed that certain diseases could be passed from afflicted to unafflicted solely by touch or by close proximity. Second, isolating a person with the disease will diminish the likelihood of contagious spread to the larger community. Third, contagiousness in the afflicted does not go on indefinitely but may abate with time. Fourth, there is a moral basis for placing the welfare of the many over the liberty of the few.
Forcibly detaining persons with alleged contagions was commonplace in many cultures, but it was not until the bubonic plague epidemic in 14th century Europe that a restrictive policy was formalized, and isolation procedures were widely undertaken. Since plague generally entered countries through their seaports, seafaring nations detained arriving vessels for extended intervals. The presumption was made that a shipboard pestilence, if present, would burn itself out during the weeks of detention. Adriatic ports, such as Venice, designated small offshore islands (called lazarets, named after the Biblical character Lazarus who had allegedly suffered from leprosy) where incoming ships were required to wait for 40 days until clearance was granted. This practice was called quarantine, from the Italian word quaranta, meaning 40. In medieval law, quarantine also designated the 40 days during which the widow may remain in her recently deceased husband’s home.
Why 40 days? The number 40 is frequently mentioned in the Scriptures as a symbolic interval of fulfillment (the duration of the flood, Moses’ 40 days on Mt. Sinai, King David’s regal tenure, Christ’s 40 days of temptation in a Judean wilderness site called Quaratania).
By the 19th century, every maritime nation had its own body of quarantine legislation and its own list of specific diseases warranting exclusion. To enter the United States at the beginning of the 20th century, for example, an immigrant had to be visibly free of tuberculosis, trachoma, venereal diseases and a number of specified communicable diseases.
International commerce increased so dramatically during the 19th century that nations began to view quarantine as an impediment to trade. Furthermore, when commerce had been conducted by sailing vessels, the transit time between ports was often measured in weeks or months, and an epidemic illness aboard ship would surely have made itself evident before landfall. But as steam-powered vessels replaced sailing ships, the interval between ports was reduced to days. Thus, for example, a person who recently contracted smallpox (with an incubation period of about 14 days) might embark in England and land 10 days later in New York without showing evidence of the disease until he was days beyond the quarantine station.
Great Britain’s General Board of Health, in its 1849 report to Parliament, declared quarantines and sanitary cordons to be signal failures, particularly since diseases such as yellow fever and cholera did not seem to be communicated by touch, as with smallpox.
The Board noted that cholera had arrived in Great Britain despite stringent quarantine. Furthermore, they observed that none of the nurses or physicians tending the many cholera victims contracted the disease. They also could not explain the mysterious paths taken by cholera in its spread through the cities of Britain. “Great epidemics,” declared the Board, “are governed by laws over which quarantine can exercise no control.” The true protection against pestilential disease, they declared, was not quarantine regulation but sanitary measures. Quarantining had neither scientific nor humanitarian merit and should be abandoned.
The lengthy 1849 report can best be appreciated by placing it in the context of medical knowledge at that time. The germ theory of disease had not yet been advanced. Epidemics were thought to be the consequence of noxious atmospheric irregularities (miasmas) combined with ill-defined individual susceptibilities. The answer, they declared, rested in improved hygiene and community sanitation. Although their reasoning was faulty, their health-protecting measures turned out to be reasonably successful.
It would be years before the mechanism by which these diseases spread was understood. Cholera was eventually shown to be disseminated not by touch but by contaminated drinking water, typhus – by the interpersonal migration of body lice, and yellow fever – by the intercession of a mosquito carrying the virus from the afflicted to the susceptible.
Only after quarantine had been discredited did the nations of the world finally agree, in 1909, to form an international office to monitor transnational interventions designed to suppress epidemics. It took centuries to learn that germs are not intimidated by national boundaries.
STANLEY M. ARONSON, M.D. (firstname.lastname@example.org) is dean of medicine emeritus at Brown University.