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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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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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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 ...