Genetic Analysis of Measles Viruses Isolated in the United States, 1995–1996

Abstract

Genetic analysis was conducted on 28 wild type measles viruses isolated from outbreaks or cases in the United States during 1995-1996. These viruses were members of at least 6 distinct genetic groups. However, none of these viruses was related to the group 2 viruses that were associated with the resurgence of measles in the United States between 1989 and 1992 except for a single importation from the Philippines. The sequence data support and extend previous findings showing that transmission of group 2 viruses within the United States was interrupted after 1993. The data also suggest that all measles cases that occurred in the United States in 1995-1996 were the result of importation of virus, even in instances when the source was unknown. Molecular epidemiologic studies can provide a means to measure the success of measles control programs by helping to identify the transmission pathways of the virus.

Determination of Spontaneous Mutation Frequencies in Measles Virus under Nonselective Conditions

“…A similar argument can be applied to MV. The mutation rate for MV measured here is still high enough to provide a paradox with the low replacement rate for the H gene of MV from isolates in the field (24,25). The number of replications involved in the transmissions of virus between at least 26 infected patients in an outbreak sustained over 1 year must be in the order of trillions, and multiplying this with the lowest rate determined here of 0.03 per genome replication still indicates the tremendous selection pressure that is required to explain the low replacement rate for MV in the field.…”

Update on the Global Distribution of Genotypes of Wild Type Measles Viruses

“…Analysis of viruses isolated from measles cases and outbreaks in the United Stated between 1994 and 2001 failed to detect ongoing transmission of an endemic genotype ( figure 1). Rather, the diversity of genotypes detected in the last 7 years is indicative of multiple, imported sources of virus [28,29]. Likewise, the diversity of genotypes detected in Australia, Canada, and the United Kingdom is similar to that observed in the United States, suggesting frequent importation of measles and lack of endemic circulation of virus [30][31][32][33].…”

“…Endemic transmission has been eliminated in many areas of the world, including most of the countries in the Western Hemisphere. Both virologic and epidemiologic data collected in the United States between 1989 and 2000 indicated that interruption of transmission of the genotype D3 viruses that were associated with the measles resurgence of the early 1990s was achieved in 1993 and subsequently maintained [14,28]. Analysis of viruses isolated from measles cases and outbreaks in the United Stated between 1994 and 2001 failed to detect ongoing transmission of an endemic genotype ( figure 1).…”

“…The most frequently isolated measles genotypes in Europe have been C2 and D6 [42][43][44], and genotype D7 [45] viruses have been shown to circulate widely in the western part of Germany. Because of the frequency of travel to and from Europe, genotypes C2, D6, and D7 are often associated with measles cases imported from Europe to other parts of the world [28,29,38]. Several measles genotypes have been identified in Africa.…”

“…Genotype D4 and D8 viruses have been isolated in India and Nepal, and genotype D4 was detected in Pakistan [20,54,55]. Genotype D4 viruses have also been detected in measles cases imported into the United States from both Pakistan and India [28,29]. Extensive virologic surveillance in Japan has demonstrated that genotypes D3 and D5 have been co-circulating in Japan for at least 10 years [56][57][58].…”