A genus of the family Picornaviridae. Enteroviruses include the polioviruses (three types), the coxsackieviruses (more than 29 types), and the echoviruses (more than 34 types). They are small (17–28 nanometers in diameter), contain ribonucleic acid (RNA), and are resistant to ether. In contrast to the rhinoviruses, the enteroviruses multiply chiefly in the alimentary tract and are stable under acid conditions (pH 3–5) for 1–3 h. They are protected by magnesium chloride against inactivation by heat. The polioviruses, most echoviruses, and a number of the coxsackieviruses can be grown in cell cultures of monkey origin, as well as in human cells. Certain of the coxsackieviruses will not grow in cultures; they are usually studied by infecting newborn mice. Those strains that can be grown in tissue cultures usually grow best if the cultures are kept stationary and incubated at 98.5°F (37°C).