MOLECULAR ANALYSIS OF RUBELLA-VIRUS EPIDEMIOLOGY ACROSS 3 CONTINENTS,NORTH-AMERICA, EUROPE, AND ASIA, 1961-1997

The El gene nucleotide sequences of 63 rubella virus isolates from Nor th America, Europe, and Asia isolated between 1961 and 1997 were compa red phylogenetically, Two genotypes were evident: Genotype I contained 60 viruses from North America, Europe, and Japan, and genotype II con tained 3 viruses from China and India. The genotype I isolates prior t o 1970 grouped into a single diffuse clade, indicating intercontinenta l circulation, while most post-1975 viruses segregated into geographic clades from each continent, indicating evolution in response to vacci nation programs. The El amino acid sequences differed by no more than 3%; thus, no major antigenic variation was apparent. Among 4 viruses f rom congenital rubella syndrome that occurred following reinfection, o nly one amino acid substitution occurred in several important epitopes , indicating that antigenic drift is not important in this phenomenon. However, 2 viruses isolated from chronic arthritis exhibited changes in these epitopes, Isolates of the RA 27/3 vaccine strain were readily identifiable by nucleotide sequence.