Molecular characterization of measles viruses isolated in Victoria, Australia, between 1973 and 1998

Molecular epidemiology studies have made significant contributions to the c ontrol of measles virus infection through the identification of source and transmission pathways of the virus. These studies allow observation of chan ges in measles virus genotypes over time in a particular geographical locat ion, clarification of epidemiological links during measles outbreaks, separ ation of indigenous strains from newly imported strains and distinction bet ween vaccine- and wild-type virus-associated illness, A total of 35 wild-ty pe measles viruses identified in Victoria, Australia, between 1973 and 1998 were characterized by nucleic acid sequence analysis of the nucleoprotein gene and, in some cases, the haemagglutinin gene. Relatedness between the v iruses was studied and genotypes were assigned using a classification schem e recently proposed by the World Health Organization. Five recognized genot ypes (C2, D1, D4, D5 and H) and one previously undescribed genotype, which we propose to be D7, were identified. Successive replacement of measles vir us genetic lineages occurred in Victoria, with no evidence of temporal over lap, during this 25 year period. This pattern of circulation is likely to r epresent serial importation of wild-type measles virus strains from oversea s foci of measles virus infections.