Intro
The Controversy: Control or Eradication?
We cannot refrain altogether from examining the roots of this controversy if only because the extreme views for and against eradication have exerted and are still exerting a . . . highly detrimental influence on public health practice.
—P. Yekutiel, Eradication of Infectious Diseases: A Critical Study
Eradication of an infectious disease is an extraordinary goal. Its possibility became apparent as soon as Edward Jenner demonstrated an ability to provide immunity to smallpox. Writing in 1801, Jenner observed that, through broad application of vaccination, "it now becomes too manifest to admit of controversy that the annihilation of the Small Pox, the most dreadful scourge of the human species, must be the result of this practice" (Jenner 1801). Louis Pasteur claimed that it was "within the power of man to eradicate infection from the earth" (Dubos and Dubos 1953). And yet, by and large, public health has proceeded with more modest goals of local and regional disease control. Notable successes have occurred. Indeed, some diseases now thought of as "tropical" were previously endemic in temperate climates. Systematic application of hygiene, sanitation, environmental modification, vector control, and vaccines have led, in many countries, to the interruption of transmission of microbes causing such diseases as cholera, malaria, and yellow fever.
Intensive efforts to eliminate breeding sites of the yellow fever mosquito vector, Aedes aegypti, interrupted transmission of this disease in Havana in 1901 and throughout Cuba soon thereafter. Subsequently, yellow fever and malaria were able to be controlled in Panama, thus permitting construction of the Panama Canal. In 1915, the Rockefeller Foundation launched an effort to eradicate the disease worldwide. Transmission appeared to have ceased in the Americas by 1928, but then cases reappeared, and by 1932, it became clear that a nonhuman endemic focus was serving to reinfect areas otherwise free of yellow fever. In the 1930s, F. L. Soper set out to eradicate the Aedes aegypti vector from the Americas. By 1961, Soper reported that he had largely succeeded except for the United States, where the program received little support. By the 1980s, Aedes aegypti had become reestablished in Central and South America.
In 1953, Brock Chisholm, the first director-general of the World Health Organization (WHO), tried to persuade the World Health Assembly (WHA) to undertake smallpox eradication, but a number of countries objected on the grounds that eradication was not technically feasible. Instead, in 1955, under the leadership of his successor, Marcolino Candau, WHO began a global effort to eradicate malaria primarily by means of household spraying of DDT. The relatively sophisticated science of malaria control was abandoned in favor of this simplistic technology (Jeffrey 1976). Despite an expenditure of more than US$2 billion, the effort failed.
Even while the malaria eradication effort was under way, the Soviet Union, in 1958, proposed to the WHA that smallpox be eradicated. A resolution to this effect was offered in 1959 and passed unanimously. However, the resolution provided little international funding or support. Over the next seven years, disease transmission was interrupted in some 30 countries in Africa, Asia, and South America, but endemic smallpox persisted in the Indian subcontinent, Indonesia, most of Sub-Saharan Africa, and Brazil. WHO launched an intensified effort in 1967 to eradicate the disease within a decade. This new resolution included an annual budget of US$2.4 million, to be paid according to the WHO scale of assessments. The resolution passed by the narrowest of margins, but a reinvigorated effort was soon under way and paved the way for a historic public health achievement (Henderson 1988). Following an extraordinary worldwide effort, the last case of smallpox was isolated in October 1977, and the disease was certified as being eradicated in 1979, 170 years after Edward Jenner first dreamed of that possibility. Understanding how and why smallpox eradication succeeded is essential to the study of control and eradication.
The smallpox success was inspirational, even though the leaders of WHO's smallpox eradication effort cautioned that, among all the diseases that might be considered candidates for eradication, smallpox was unique (Fenner and others 1988) and that they foresaw no other disease as a candidate for eradication (Henderson 1982). At a meeting convened by the Fogarty International Center of the National Institutes of Health in 1980, scientists, public health officials, and policy makers discussed the merits of eradicating other diseases, with schistosomiasis, dracunculiasis, poliomyelitis, and measles identified as possible candidates (aHenderson 1998a). However, no consensus was reached at that time on moving forward with any of those diseases.
Poliomyelitis became the next principal target when mass vaccination campaigns, proposed by Albert Sabin (1991), proved remarkably successfully in Cuba and Brazil. In 1985, an American Health Organization coordinated campaign was launched to interrupt poliovirus transmission in the Americas by 1991, and this effort succeeded. Some believed that global eradication might be possible, although others were concerned that the far less developed infrastructure of health, transportation, and communications services in many parts of Asia and Africa would make it an unachievable task. In 1988, the WHA adopted a resolution to eradicate polio, but at that time, a longer-term strategy for ending polio vaccination was neither formulated nor agreed on by the public health and scientific community.
The WHA has adopted only one other resolution to eradicate a disease—guinea worm, or dracunculiasis. The eradication of this disease can be achieved by applying simple technologies for providing water that is free of the vector copepod and parasite and for treatment of patients with the disease. This eradication program has made steady progress but has been hampered in part by civil and political unrest and lack of program priority because of low mortality and low incidence in some remaining endemic areas. However, given the environmental restriction of the parasite to rural tropical areas and its relatively low transmissibility, eventual global eradication seems within reach.
One other case—that of measles—is worth noting. A number of public health authorities have raised the possibility of eradicating that disease. In the Americas, spurred on by the success of regional cessation of transmission of wild poliovirus, eventual consensus was reached to intensify measles control efforts, primarily through surveillance and periodic pulse application of measles vaccine in national campaigns. As a consequence, transmission of measles virus was temporarily interrupted in the Americas on several occasions but reestablished again by importations (CDC 1998a). Although the U.S. Centers for Disease Control and Prevention (CDC) and WHO have advocated extending measles "elimination" through vaccination campaigns and second-dose opportunities to other regions (Biellik and others 2002; CDC 1998a; 1998b, 1999a, 1999b, 2003d, 2004b, 2004d, 2004f), the intensive control efforts required to break transmission of this highly infectious agent make global eradication unlikely at this time.
