Evolution
This virus is a member of the enterovirus species A. This virus appears to have evolved only recently with the first known strain isolated in 1965. It was associated with an outbreak of neurological disease in the United States in 1969. It spread then to Europe with outbreaks there in Bulgaria (1975) and Hungary (1978). It has since spread to various countries in Asia where it has been responsible for several outbreaks, most recently in Cambodia (2012).
The strains fall into three taxa - named A, B and C. Both the B and C clades have been subdivided into B1-B5 and C1-C5. The C taxon appears to have evolved ~1970 while the A and B taxa evolved prior to this.
An analysis of strains isolated in Europe (Austria, France and Germany) showed that the clades C1b and C2b originated in 1994 (95% confidence interval 1992.7-1995.8) and 2002 (95% confidence interval 2001.6-2003.8) respectively.
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