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The Enteroviruses constitute a genus within the Picornaviridae family of viruses. As their family name implies, these viral agents are small (ie, “pico”), ribonucleic acid (RNA) genome (ie, “rna”), viruses (ie, “viridae”). Traditionally, the genus Enterovirus was speciated into 5 groups: polioviruses, Coxsackie A viruses, Coxsackie B viruses, echoviruses, and numbered enteroviruses (Table 306-1).

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Table 306-1. The Human Enteroviruses
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The current taxonomic classification of the enteroviruses is based on molecular and biologic characteristics of the viral isolates and divides the enteroviruses into 5 species: polioviruses and human enteroviruses A–D (Table 306-1).17 There are currently 68 recognized enteroviral serotypes. An additional 16 enterovirus serotypes await official recognition.

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Morphologically, the enteroviruses are icosahedral-shaped virions that lack an envelope and measure 30 nm in diameter. The capsid is composed of 60 units each of 4 viral capsid proteins: VP1, VP2, VP3, and VP4. They are acid-, ether-, and chloroform-stable and insensitive to nonionic detergents. The enterovirusesare inactivated by heat (> 56°C), ultraviolet light, chlorination, and formaldehyde. These physical and chemical characteristics confer environmental stability to the enteroviruses, permitting them to survive for days to weeks in water and sewage.

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Epidemiology

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The enteroviruses are ubiquitous agents with a worldwide distribution. Enteroviral infections exhibit a strong seasonal epidemiology. In regions with temperate climates, the majority of enterovirus infections occur during the summer and early fall.30-32 In the United States, approximately 80% of reported nonpolio enterovirus infections occur from June to October, with the peak incidence of disease occurring in August.32 Enterovirus infections continue to occur during the winter but with significantly less frequency than during the warmer months of the year.33-36 In the world’s tropical regions, enterovirus infections occur year round or with increased incidence during the rainy season.37

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In the United States and the Americas, as a result of effective vaccination programs against the polioviruses, these members of the genus no longer circulate ...

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