CLUSTERING OF MUMPS-VIRUS ISOLATES BY SH GENE SEQUENCE ONLY PARTIALLYREFLECTS GEOGRAPHICAL ORIGIN

The nucleotide sequences of the SH gene of 45 new mumps virus isolates derived from different parts of Europe, Canada and USA were determine d. A phylogenetic tree was constructed which confirmed the existence o f three major clusters. While clustering according to geographical ori gin was clear in some cases each of the major clusters included isolat es which were widely separated in origin. The degree of variability be tween the sequences of SH genes of different strains and the ratio of coding to non coding differences were both very high compared to those observed in other genes such as the M and HN. A standardized system o f nomenclature of mumps strains was established.