Echoviruses were originally isolated from the feces of an indi-vidual who had no clinical illness and caused a cytopathic effect in the cell culture. The prefix ECHO is an acronym for enteric cytopathogenic human orphan viruses (ECHO viruses).They were earlier called “orphans”, because these viruses were not associated earlier with any disease but now they are known to cause a variety of human illnesses.
The echoviruses resemble other enteroviruses in their properties. They are classified into 32 serotypes (1–34 except 10 and 28) on the basis of their type-specific neutralization cap-sid antigen. Some serotypes of echoviruses (types 3, 6, 7, 11, 12, 13, 19, 20, 21, 24, 29, 30, and 33) cause hemagglutination of human red cells. Agglutination of red cells is followed by elu-tion, making the red cells inagglutinable by echoviruses or cox-sackieviruses but not by myxoviruses.
All echoviruses grow in human and monkey kidney cell lines, producing cytopathic effects. Humans are the natural hosts for these viruses. Echoviruses are found in the intestinal tract of the infected humans. The infection like other enterovirus is transmitted by fecal–oral route.
Most of the echoviruses cause asymptomatic infections in humans, but some of them have been associated with many clinical syndromes. Nonspecific febrile illness associated with rash, headache, and common-cold-like symptoms is caused by many serotypes of echoviruses. Aseptic meningitis is also caused by echoviruses. Some strains of echovirus have been associated with gastroenteritis (serotype 8) and respi-ratory diseases in children (serotypes 1, 11, 19, 20, and 22).
Laboratory diagnosis of echovirus infection is made by isolation of viruses from feces, throat swab, or CSF. They are cultured using human diploid embryonic lung fibroblast and human rhabdomyosarcoma cell lines. The growth of the virus is detected by cytopathic changes, which is similar to that of other coxsackieviruses.