Etiology
Enteroviruses, single-stranded RNA viruses within the Picornaviridae family, are responsible for a number of human diseases. Enteroviruses are closely related to rhinoviruses, and both belong to the genus Enterovirus. There are more than 100 nonpolio human enteroviruses, divided into four major species designated as enterovirus A, B, C and D. The nonpolio enteroviruses often cause mild illness without distinctive clinical features and are a leading cause of the “summer cold.” In addition, enteroviruses may be associated with specific clinical syndromes such as hand-foot-and-mouth disease, herpangina, conjunctivitis, hepatitis, myocarditis, neonatal sepsis, meningitis, encephalitis, and acute flaccid myelitis. Outbreaks caused by nonpolio enteroviruses occur on a regular basis, and multiple strains may circulate simultaneously.
Pathophysiology
Enteroviruses and rhinoviruses are typically distinguished based on the temperature at which they grow and their sensitivity to acid treatment. Enteroviruses generally live within the gastrointestinal tract, and are adapted to grow best under acidic conditions and at body temperature. In contrast, rhinoviruses thrive within the cooler environment of the nose and the upper respiratory tract, and are very sensitive to acidity. Unlike most enteroviruses, enterovirus D68 (EV-D68) behaves more like a rhinovirus, and is both sensitive to acid treatment and grows best at 91.4°F (33°C), the temperature within the nose.[32][33] Viremia has been reported in children with EV-D68 and pneumonia, and this may provide a mechanism by which systemic disease can occur.[34]
Classification
National Center for Biotechnology Information (NCBI) taxonomy database[14]
EV-D68 is one of more than 100 nonpolio enteroviruses. Molecular sequencing demonstrated that EV-D68 is identical to human rhinovirus type 87.
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