Enteroviruses: Polio
Poliomyelitis (polio), the much-feared crippling epidemic disease of the twentieth century, is on the verge of eradication. Before introduction of the inactivated poliovirus vaccine (IPV) in 1955 and the oral poliovirus vaccine (OPV) in 1961, polio had ne
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Olen M. Kew
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Introduction
Six decades ago, every child faced the threats of lifelong paralysis or death from poliomyelitis. Poliomyelitis, an infectious disease dating back to antiquity (Fig. 13.1), suddenly appeared in epidemic form in the late nineteenth century in northern Europe and the United States and emerged as one of the great epidemic diseases of the twentieth century [1–3]. The threat of poliomyelitis quickly receded in developed countries following the introduction of the inactivated poliovirus vaccine (IPV) in 1955 [4, 5] and the oral poliovirus vaccine (OPV) in 1961 [6, 7] and had all but disappeared in high-income countries by the early 1970s [8, 9]. In sharp contrast, poliomyelitis remained largely uncontrolled in the developing countries of Latin America, Asia, and Africa and continued to threaten the majority of the world’s children with crippling disease [8, 9]. Today, poliomyelitis is on the verge of eradication, and its etiologic agents, the three poliovirus serotypes, are on the brink of extinction from the natural environment (Figs. 13.2 and 13.3) [12]. Circulation of indigenous wild type 2 poliovirus ceased in 1999 [13], and wild type 3 poliovirus may be nearing eradication [12]. Wild type 1 poliovirus circulation is localized to a small and decreasing number of districts in parts of three countries (for updates see http://www.polioeradication.org/) [12]. This brightening picture is the direct result of the initiatives launched in 1985 by the Pan American Health Organization (PAHO; the Regional WHO Office for the Americas) to eradicate poliomyelitis in the Americas by 1990 [14], and subsequently by the World Health Organization (WHO) to eradicate poliomyelitis worldwide by the year 2000 [15]. The Global Polio Eradication
O.M. Kew, PhD Polio and Picornavirus Laboratory Branch, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30329-4018, USA e-mail: [email protected]
Initiative (GPEI), established by a landmark 1988 resolution of the World Health Assembly (the governing body of the WHO) [15], has grown to become the largest public health program in history [16], engaging key segments of both the public and private sectors [17]. The launch of the GPEI was made in light of dramatic progress by PAHO toward achieving its regional eradication goal, attained in 1991 [18]. Like the PAHO initiative, the GPEI achieved early rapid progress, reducing poliomyelitis incidence worldwide by >99 %, from an estimated 350,000 cases in 125 countries in 1988 to a low of 493 cases reported in 10 countries in 2001, raising the long-held hope that a polio-free world would soon be realized [19]. Optimism was fueled by the eradication of wild poliovirus type 2 and reinforced by the cessation of wild poliovirus transmission in many highly challenging settings. However, progress stalled between the years 2000 and 2010 as the global incidence poliomyelitis stabilized at ~500–2,000 cases per year (Fig. 13.2a) [10, 19, 20
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