Theenterovirusesareagenusof(+)ssRNAvirusesassociatedwithseveralhumanandmammaliandiseases.HistoricallythemostsignificanthasbeenthePoliovirus.Othertypesarecoxsackieandechovirus.Enterovirusarethemostcommoncauseofasepticmeningitisandcancauseseriousdiseaseespeciallyininfantsandtheimmunocompromised.Humanenteroviruses(familyPicornaviridae)infectmillionsofpeopleworldwideeachyear,resultinginawiderangeofclinicaloutcomesrangingfromunapparentinfectiontomildrespiratoryillness(commoncold),hand,footandmouthdisease,acutehemorrhagicconjunctivitis,asepticmeningitis,myocarditis,severeneonatalsepsis-likedisease,andacuteflaccidparalysis.IntheUnitedStates,enterovirusesareresponsIBLefor30,000to50,000meningitishospitalizationsperyearasaresultof30millionto50millioninfections.SEROlogicstudieshavedistinguished66humanenterovirusserotypesonthebasisofanantibodyneutralizationtest,andadditionalantigenicvariantshavebeendefinedwithinseveraloftheserotypesonthebasisofreducedornonreciprocalcross-neutralizationbetweenprototypeandvariantstrains.Onthebasisoftheirpathogenesisinhumansandexperimentalanimals,theenteroviruseswereoriginallyclassifiedintofourgroups,polioviruses,coxsackieAviruses(CA),coxsackieBviruses(CB),andechoviruses,butitwasquicklyrealizedthatthereweresignificantoverlapsintheBIOLOGicalpropertiesofvirusesinthedifferentgroups.Themorerecentlyisolatedenteroviruseshavebeennamedwithasystemofconsecutivenumbers:EV68,EV69,EV70,andEV71.