GLOBAL ERADICATION OF SMALLPOX

12 May

Although smallpox killed more than 15 million people a year during the 1950s, by the 1960s, for most residents of the wealthy industrialized nations, the odds of suffering ill effects from vaccination became greater than the chance of encountering smallpox. However, given the extensive and rapid movement of people in the Jet Age, as long as smallpox existed anywhere in the world, the danger of outbreaks triggered by imported smallpox could not be ignored. For the United States, Great Britain, and the Soviet Union, the worldwide eradication of smallpox offered a humane and economical solution to the vaccination dilemma. The World Health Organization adopted the Smallpox Eradi- cation Program in 1958, but the intensive campaign for global eradi- cation was not launched until 1967, when smallpox was endemic in 33 countries and another 11 reported only imported cases. Despite the availability of large stocks of donated vaccine, few public health special- ists were optimistic about the possibility of eradicating smallpox from the world’s least developed nations, with their negligible medical resources and overwhelming burden of poverty and disease. Surprisingly, within four years, 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, the smallpox eradication strategy called for mass vacci- nation using jet immunization guns that could deliver hundreds of doses per hour. In order to eradicate smallpox in any given nation, epidemiol- ogists considered it necessary to vaccinate 80 to 100 percent of the population. Public health workers soon encountered virtually insur- mountable difficulties in maintaining stocks of vaccine and injector guns under primitive conditions in hot, humid climates. Simpler equipment, like the bifurcated needle (two-pronged), proved to be more reliable and efficient.

As a result of shortages of personnel and equipment in eastern Nigeria, public health workers discovered, almost by accident, that a strategy called ‘‘surveillance-containment’’ effectively broke the chain of transmission. By concentrating limited resources on the most infected areas, the new strategy was successful even when only 50 per- cent of the population had been vaccinated. In October 1977, Ali Maow Maalin of Somalia became the last person to contract smallpox outside a laboratory setting. The case might have spelled disaster for the con- tainment program. Maalin worked as a cook in a busy city hospital and his disease was first misdiagnosed as malaria and later as chicken pox. During the most contagious stage of the disease, Maalin had more than 160 contacts, but no other cases of smallpox occurred. Although humanitarian motives were not absent from the decision to declare a global war against smallpox, there is no doubt that eco- nomic factors loomed large in the choice of this target. Global eradi- cation of smallpox cost billions of dollars, but, by eliminating the disease, sponsors of the campaign against smallpox were liberated from the threat of imported cases, without imposing the dangers of vacci- nation on their own people. For developing nations, malaria and other so-called 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 resistance to other infections, productivity, and the live birth rate. The December 1979 Final Report of the Global Commission for the Certification of Smallpox Eradication solemnly declared that: ‘‘The world and all its peoples have won freedom from smallpox.’’ At the end of the eradication program, WHO and a number of countries independently stored enough smallpox vaccine for 60 million people and a supply of the vaccinia virus that could be used to make vaccine. During the 1980s the practice of vaccination was essentially abandoned throughout the world, except for a few special cases, such as scientists conducting research on vaccinia or various poxviruses. In the United States, routine smallpox vaccinations for children ended in 1972; the military continued to recommend vaccinations until the late 1980s. In describing the successful completion of the Smallpox Eradication Pro- gram, Donald A. Henderson, director of the Eradication Program from 1966 to 1977, proposed the next logical step: what had been learned in the smallpox campaign should form the basis of global immunization programs for controlling diphtheria, whooping cough, tetanus, measles, poliomyelitis, and tuberculosis. Such global campaigns could transform the mission of health services ‘‘from curative medicine for the rich to preventive medicine for all.’’ After the terrorist attacks of September 11, 2001, Henderson became the director of the United States Office of Public Health Emer- gency Preparedness and Response. Finding the world in danger of ‘‘regressing’’ in the battle against a disease that was presumably eradi- cated in the 1970s, Henderson expressed the frustration and sorrow of those who had once envisioned an era of global disease control pro- grams. In addition to a distinguished career in the Departments of Epidemiology and International Health in the School of Public Health at Johns Hopkins, Henderson became founding director of the Johns Hopkins Center for Civilian Biodefense Studies. His federal appoint- ments include Associate Director of the Office of Science and Tech- nology Policy, Executive Office of the President, Deputy Assistant Secretary and Senior Science Advisor to the Department of Health and Human Services on civilian biodefense issues, and Chairman of the National Advisory Council on Public Health Preparedness. His many awards and honors include the National Medal of Science, the Presidential Medal of Freedom, and the Royal Society of Medicine’s Edward Jenner Medal.

At the time that global eradication of smallpox had been achieved, the only known reservoirs of smallpox virus were samples held, deliberately or inadvertently, by an unknown number of research laboratories. The danger of maintaining such laboratory stocks was exposed in 1978 when Janet Parker, a 40-year-old medical photographer who worked in the Birmingham University Medical School, contracted smallpox. The virus apparently entered rooms on the floor above a virus research laboratory through air ducts. Parker was hospitalized and diagnosed 13 days after becoming ill; she died two weeks later. About three hundred people who had come in contact with her were quarantined. Her father died of a heart attack after visiting her. Parker’s mother contracted smallpox, but she recovered. The accident also led to the death of Henry Bedson, the 49-year-old director of the virus research laboratory. After confirming the source of the virus that had killed Parker, Bedson wrote a note admit- ting that he had ignored safety precautions while conducting research. Overwhelmed by guilt, Bedson committed suicide. His laboratory was due to close at the end of the year, because inspectors considered it too old and unsafe to be used for smallpox research. Virologists have noted that, in addition to illicit laboratory stocks, potentially viable smallpox virus might still persist in ancient crypts and coffins, or in cadavers in the permafrost of the Siberian tundra. With the threat of naturally occurring smallpox eliminated, fears have grown that the virus could be used as an agent of bioterrorism or germ warfare. Nations that were smallpox-free when the global cam- paign began generally abandoned their own vaccination programs in the 1970s, leaving new generations to confront the possibility that terrorists or rogue nations might obtain stocks of smallpox virus. Smallpox has been called the ideal agent for germ warfare because the virus is stable, easy to grow, easily disseminated, and, above all, causes a terrifying, highly contagious, and often fatal disease. Terrorists might utilize ‘‘human missiles’’ or ‘‘smallpox martyrs’’—people infected and sent out to spread virus by coughing and sneezing in populous areas during the most infectious phase of the disease. Progress in molecular biology has added the possibility that terrorists might develop novel or geneti- cally modified pathogens, including vaccine-resistant smallpox strains. Revelations about the germ warfare programs carried out in the former USSR emphasized the potential dangers of weaponized patho- gens. Information about the Soviet germ warfare program, including the development of weaponized smallpox, was provided by Kanatjan Kalibekov (also known as Ken Alibek), a scientist who defected to the United States in 1992. Alibek also warned that unemployed scien- tists might have sold stocks of the virus during the collapse of the Soviet Union. Later, Alibek attempted to reach a wider audience with his book Biohazard (1999), a landmark in the modern literature on biological weapons. A report released in 2002 suggested that a Soviet field test of weaponized smallpox might have caused an outbreak in Aralsk, a port city in Kazakhstan, in 1971. Ten people contracted smallpox and three unvaccinated people died of the hemorrhagic form of the disease. The seven survivors had previously received routine vaccinations. Emergency teams quarantined hundreds of people and administered almost 50,000 vaccinations in less than two weeks. In addition to worrying about the threat that bioterrorists might use smallpox as a weapon, virologists worry about the possible emer- gence of new or previously rare viral diseases, such as monkeypox, which was first discovered in the 1950s in monkeys from Zaire. The monkeypox virus is actually more commonly found in squirrels, mice, and other small rodents in western and central Africa.

Although mon- keypox virus is not readily transmitted to or among people, hundreds of sporadic human cases have been recorded; the fatality rate among reported cases is about 10 percent. Vaccination seems effective against monkeypox, but in areas of Africa where the virus occurs, AIDS is widespread today, which means many people could not be vaccinated. Until 2003, monkeypox had been reported only in Africa, but more than 70 suspected cases occurred in the United States in 2003. The virus reached the United States in Gambian giant pouched rats, which were shipped from Ghana to American pet stores. The demand for exotic pets has allowed the exchange of pathogens between different species and the subsequent infection of human beings. Since September 11 and the anthrax attacks, people tend to think that the sudden appear- ance of any exotic disease might be the result of bioterrorism, but the trade in exotic pets and live-animal-food markets must also be considered. All stocks of the smallpox virus were supposedly destroyed by 1984, except for virus kept at two official depositories: the Atlanta headquarters of the Centers for Disease Control and Prevention and at a Russian government laboratory in Novosibirsk, Siberia. Since the eradication of smallpox, the WHO has debated the fate of the last official smallpox virus stocks. In the 1990s, the World Federation of Public Health Associations and the World Health Assembly called for the destruction of all remaining smallpox virus. The WHO planned to destroy the last official stocks of the virus in 2002, but the scheduled execution was delayed. Some scientists opposed destroying the last viral stocks because of the possibility that research might lead to new drugs and vaccines. Scientists thought that the smallpox virus could attack only humans, but in 2001 researchers were able to infect monkeys with a particularly virulent strain of the virus. With an animal model, scientists could conduct previously impossible studies of antiviral drugs, vaccines, biosensing systems, virulence factors, host speci- ficity, and so forth.

Many experts on biological weapons believe that Iraq, Iran, North Korea, and perhaps other nations or terrorist groups might already have clandestine stocks of the virus. In response to the growing concern for bioterrorism since September 11, 2001, and the anthrax attacks in 2001, public health experts began to reconsider the need for vaccination, especially for potential ‘‘first responders’’ to terrorist attacks. Few public health experts favor a return to mass vaccinations, given the pre- sumably small risk of uncontrollable outbreaks and the known risks of severe, even lethal, reactions to the vaccine. Perhaps one or two out of every million people vaccinated might die and a few hundred out of every million could have severe reactions. A vaccinated person could infect others, causing severe infections. Vaccination would not be recommended for people with AIDS and other conditions that damage the immune system, and people with skin disorders like eczema, atopic dermatitis, and acne. Scientists also fear that existing vaccines might not be effective against a new bioengineered strain of smallpox virus. If terrorists wanted a weapon that rapidly killed large numbers of people, smallpox would be a poor weapon. But the fact that significant parts of the U.S. government and the post office were all but paralyzed in 2001 by a few envelopes containing anthrax spores, suggests that the threat of smallpox, even more than the reality of the disease, would make it an ideal tool for terrorists whose major objective is to frighten and demoralize people.

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