Molecular epidemiology of measles virus: identification of pathways of transmission and implications for measles elimination.

The nucleotide sequences of either the hemagglutinin or nucleoprotein genes from wild type measles viruses isolated in the United States between 1989 and 1992 differed by < 0.5%. This suggests that the majority of viruses associated with resurgence of measles in the United States belonged to a single indigenous genotype. In contrast, wild type viruses isolated from sporadic outbreaks of measles in the United States during 1994 were genetically heterogeneous. These viruses were more closely related to wild type viruses previously circulating in Europe, Africa, or Japan and were epidemiologically linked to importations or no known source. In addition to demonstrating the utility of genetic analysis in understanding the epidemiology of measles, these data suggest that the transmission of the indigenous virus was interrupted after the 1989-1992 epidemic. Measures to further reduce the incidence of measles in the United States should include efforts to control importation and subsequent spread of measles.