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

Molecular epidemiology studies have made significant contributions to the control of measles virus infection through the identification of source and transmission pathways of the virus. These studies allow observation of changes in measles virus genotypes over time in a particular geographical location, clarification of epidemiological links during measles outbreaks, separation of indigenous strains from newly imported strains and distinction between vaccine- and wild-type virus-associated illness. A total of 35 wild-type 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 viruses was studied and genotypes were assigned using a classification scheme recently proposed by the World Health Organization. Five recognized genotypes (C2, D1, D4, D5 and H) and one previously undescribed genotype, which we propose to be D7, were identified. Successive replacement of measles virus genetic lineages occurred in Victoria, with no evidence of temporal overlap, during this 25 year period. This pattern of circulation is likely to represent serial importation of wild-type measles virus strains from overseas foci of measles virus infections.