Encephalomyocarditis virus (EMCV) was isolated for the rst time in 1945 in Miami, Florida, from a captive chimpanzee and a gibbon that died suddenly of pulmonary edema and myocarditis . Mice inoculated with a ltered edema uid from the gibbon or the chimpanzee displayed paralysis of the posterior members and myocarditis followed by death in a week. The pathogenic agent was at that time given the name of EMCV. The virus had probably been transmitted from wild rats living in proximity to the monkeys, as nearly 50% of the captured rats had antibodies against EMCV. In 1948, in the Mengo district of Uganda, Dick et al.  isolated Mengo virus from a captive rhesus monkey that had developed a posterior member paralysis. In 1949, cross-neutralization studies showed that Mengo virus, EMCV, Columbia-SK (discovered in 1939), and MM (discovered in 1943) were antigenically indistinguishable but differed from Theiler’s murine encephalomyelitis virus (TMEV) . Following the Panama epizooty of 1958, Murnane et al.  described the isolation of EMCV from swine for the rst time. Since then, the virus has been isolated in many countries, in swine and in wild animals.