The Global Eradication of Smallpox

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The Global Eradication of Smallpox

Overview

Smallpox is an acute, highly contagious, and often lethal disease caused by a virus that may be airborne but that can also be spread by direct contact or by clothing and bedding contaminated by pus and scabs. In 1979 after two years without a reported case, the World Health Organization (WHO) announced the global eradication of smallpox. The World Health Assembly continued to monitor the status of smallpox and in 1980 confirmed that the world was indeed free of the disease. The international campaign to eradicate smallpox, launched by WHO in 1967, is one of the greatest achievements of twentieth-century public health medicine and a model of international cooperation. The first steps toward the eradication of smallpox were taken in the eighteenth century, when the possibility of controlling the threat of smallpox through inoculation and vaccination was first seriously considered. By the 1970s, wealthy nations were generally abandoning routine vaccination as the threat of epidemic smallpox diminished. Because the smallpox virus could still become an agent of biological warfare or a terrorist threat, to remember and analyze the devastation formerly caused by this ancient epidemic disease is essential.

Background

The origin of smallpox is unknown, but it may have evolved from one of the pox viruses of wild or domesticated animals in Africa or Asia. Eventually, migration, warfare, conquest, and commerce carried the virus to all parts of the world. Once an individual has been infected, the virus multiplies rapidly and spreads to the internal organs. Accurate diagnosis is virtually impossible during the early stages of the disease while the patient suffers from fever, aches, sneezing, nausea, fatigue, and other flu-like symptoms. By the time the characteristic skin lesions and high fever appear, the victim may have transmitted the infection to many others. Blood poisoning, pneumonia, blindness, and deafness were not uncommon complications but, even in mild cases, smallpox pustules generally caused scarring. The form of the disease known as black, or hemorrhagic, smallpox is almost always fatal.

Various folk practices, such as exposing children to a person with a mild case of the disease, taking material from smallpox pustules and inserting it into a cut in the skin, or inhaling a powder made from dried smallpox scabs, evolved as attempts to mitigate the threat of the disease. Credit for bringing smallpox inoculation to the attention of the medical world is generally attributed to Lady Mary Wortley Montagu (1689-1762) in England and Cotton Mather (1663-1728) in colonial New England. Lady Mary observed the Turkish method of inoculation while her husband was ambassador to the Turkish court at Constantinople. Fluid was collected from pox lesions on the 12th day of the illness. The fluid was then kept warm until a patient was inoculated with it through a scratch on the skin. This produced a milder, but usually survivable, form of the disease. The Reverend Cotton Mather learned about the practice from a young African slave. He also read an account of the Turkish method in the Philosophical Transactions (1714) of the Royal Society. When a smallpox epidemic struck Boston in 1721, Dr. Zabdiel Boylston and Mather experimented with inoculation. Although the procedure was very controversial, Boylston's statistical evidence demonstrated that the mortality rate for inoculated smallpox was significantly lower than that for the naturally acquired disease. Inoculation had important ramifications for medical practitioners, public health officials, and parents who had to assess the risks and benefits of inoculation.

By the second half of the eighteenth century, inoculation was a generally accepted medical practice. Even a person with inoculated smallpox, however, was a danger to others and needed isolation and medical attention. In 1798 Edward Jenner (1749-1823) published his studies of vaccination, a safer method of gaining immunity to smallpox. Jenner explained that English milkmaids sometimes acquired the cowpox lesions and experienced minor illness. This experience provided immunity against both natural and inoculated smallpox. Jenner proved that immunity could also be transmitted directly from person to person. To distinguish between the old practice of inoculation with smallpox material and his new method, Jenner coined the term "vaccination" (from the Latin vacca, for "cow").

Although vaccination rapidly replaced inoculation, debates about the safety and efficacy of preventive vaccines have raged ever since the first experiments with smallpox. Nineteenth-century critics objected to the enactment of compulsory vaccination laws, while advocates predicted that if all states adopted compulsory vaccination, smallpox would soon disappear. At the beginning of the twentieth century, epidemiologists warned that the rate of vaccination in the United States was worse than that of all other civilized nations. After World War II, the enforcement of vaccination laws improved dramatically and smallpox was no longer considered endemic in either Britain or the United States. Nevertheless, imported cases continued to touch off minor epidemics as well as major panics. Because the disease was so rarely seen in England, the rest of Europe, or the United States, smallpox patients often infected hospital personnel, patients, and visitors before the proper diagnosis was made. Once an out-break was identified, some cities launched heroic vaccination campaigns. For example, after a smallpox outbreak in 1947, five million New Yorkers were vaccinated within two weeks.

Impact

By the 1970s, the odds of suffering ill effects from vaccination for most residents of the wealthy industrialized nations became greater than the chance of encountering smallpox itself. In 1971 the U.S. Public Health Service recommended ending routine vaccination because six to eight children died each year from vaccination-related complications. Given the extensive and rapid movement of people made possible by modern transportation, however, the danger of outbreaks triggered by imported smallpox could not be ignored as long as smallpox existed anywhere in the world. For the United States, Great Britain, and the Soviet Union, then, the worldwide eradication of smallpox offered a humane and economical solution to the vaccination dilemma.

The Smallpox Eradication Program was first adopted by the World Health Organization in 1958, but the intensive campaign for global eradication was not launched until 1967, at which time smallpox was still endemic in 33 countries. (In 1966 smallpox had killed 10 to 15 million people.) Epidemiologists agreed that smallpox was a good candidate for eradication because the disease has no animal reservoir, humans are the only hosts, and there is no carrier state or subclinical infection. Nevertheless, public health specialists were generally pessimistic about the possibility of eradicating smallpox from the world's poorest nations. Surprisingly, within a short period eradication programs in West and Central Africa were successful. During this phase of the global campaign, public health workers learned to modify their strategy in ways appropriate to special challenges. Originally, epidemiologists thought that vaccinating almost the entire population of endemic areas would be necessary. As a result of shortages of personnel and equipment in eastern Nigeria, however, public health workers there discovered that a strategy called "surveillance-containment" effectively broke the chain of transmission. By concentrating limited resources on the most infected areas and replacing expensive jet injectors with a simple bifurcated needle, the new strategy proved effective, even when only 50% of the population had been vaccinated. Finally, in October 1977, Ali Maow Maalin of Somalia became the last person outside a laboratory to contract smallpox.

Although humanitarian motives were not absent from the decision to declare war against smallpox, there is no doubt that economic factors loomed large in the choice of this target. For developing nations, malaria and other tropical diseases caused more serious problems than smallpox. Most victims of smallpox die or recover within a matter of weeks and in areas where the disease was endemic it was usually just one of many "childhood illnesses." In contrast, malaria is a debilitating, recurrent illness that reduces productivity, resistance to other infections, and the live birth rate. Global eradication of smallpox cost billions of dollars but wealthy smallpox-free nations could save even more by eliminating the threat of imported smallpox.

When the World Health Organization announced the victory over smallpox, Dr. Donald A. Henderson, who had led the campaign, urged all nations to use the lessons they had learned in the battle against smallpox to formulate and implement global immunization programs against diphtheria, whooping cough, tetanus, measles, poliomyelitis, and tuberculosis. Henderson later served as a White House science advisor and dean of Johns Hopkins School of Public Health. In the 1990s Henderson felt that it was necessary to warn politicians, scientists, and public health authorities about the potential use of the smallpox virus and other dangerous microbes for germ warfare and acts of biological terrorism. The idea that smallpox could be used in such a destructive manner is quite ancient; in colonial America, settlers and British agents were accused of deliberate attempts to cause smallpox outbreaks among Indian tribes.

With the global eradication of naturally occurring smallpox, the only reservoirs of the virus were those remaining in research laboratories. The danger of maintaining such laboratory stocks was emphasized in 1978, when a photographer working at the Birmingham University Medical School died of smallpox. The director of the laboratory committed suicide after admitting that safety precautions had been ignored. Subsequently, according to WHO, the only remaining stocks of smallpox virus were in high-containment laboratories at the Centers for Disease Control and Prevention in Atlanta and the Institute for Viral Preparations in Moscow.

At its annual meeting in 1995, the World Federation of Public Health Associations called for the destruction of all remaining smallpox virus and urged the World Health Assembly to require the destruction of all remaining stocks of smallpox virus and related materials. The following year, the World Health Assembly recommended that the last smallpox stocks be destroyed by 1999.

The smallpox virus has been called the ideal agent for germ warfare because it is simple to grow, stable, easily aerosolized, highly contagious, and causes a terrifying, often fatal illness. Moreover, the threat would be greatest to the wealthy nations that had abandoned vaccination in the 1970s. A scenario commonly envisioned by those who have studied the potential for bioterrorism involves the contamination of an airplane with smallpox virus. Many of the passengers would become infected and would carry the disease with them to their various destinations. Few American doctors would be able to diagnose smallpox, even when patients were in the advanced stages of the disease. Smallpox outbreaks could thereby overwhelm medical facilities.

Speaking at the International Conference on Emerging Infectious Diseases in March 1998, Henderson warned his audience that the United States lacked the infrastructure, planning, and funding to deal with the threat of biological terrorism. Henderson pointed out that the kinds of microbes that might be used by bioterrorists—smallpox, anthrax, and plague—would be virtually unknown to the American medical community. Experts in bioterrorism argue that preparation would act as a deterrent to the use of biological weapons and have called for the development and implementation of strategic plans for coping with bioterrorism and biological warfare.

Moved by such warnings, President Bill Clinton approved new directives to improve the country's ability to prevent as well as respond to chemical and biological attacks, and the Department of Health and Human Welfare announced that it was working with other federal and military agencies to address the threat of bioterrorism. The Institute of Medicine and the National Research Council established a committee to investigate research and development strategies that would be useful in minimizing the damage caused by potential bioterrorist attacks. New drugs and vaccines to combat anthrax and smallpox were among the projects noted in the committee's report, Chemical and Biological Terrorism: Research and Development to Improve Civilian Medical Response, which was released in 1998.

LOIS N. MAGNER