The enteroviruses are a genus of (+)ssRNA viruses associated with several human and mammalian diseases. Historically the most significant has been the Poliovirus. Other types are coxsackie and echovirus. Enterovirus are the most common cause of aseptic meningitis and can cause serious disease especially in infants and the immunocompromised. Human enteroviruses (family Picornaviridae) infect millions of people worldwide each year, resulting in a wide range of clinical outcomes ranging from unapparent infection to mild respiratory illness (common cold), hand, foot and mouth disease, acute hemorrhagic conjunctivitis, aseptic meningitis, myocarditis, severe neonatal sepsis-like disease, and acute flaccid paralysis. In the United States, enteroviruses are responsible for 30,000 to 50,000 meningitis hospitalizations per year as a result of 30 million to 50 million infections. Serologic studies have distinguished 66 human enterovirus serotypes on the basis of an antibody neutralization test, and additional antigenic variants have been defined within several of the serotypes on the basis of reduced or nonreciprocal cross- neutralization between prototype and variant strains. On the basis of their pathogenesis in humans and experimental animals, the enteroviruses were originally classified into four groups, polioviruses, coxsackie A viruses (CA), coxsackie B viruses (CB), and echoviruses, but it was quickly realized that there were significant overlaps in the biological properties of viruses in the different groups. The more recently isolated enteroviruses have been named with a system of consecutive numbers: EV68, EV69, EV70, and EV71.