Genetic characterization of wild-type measles viruses isolated in China, 2006-2007

Molecular characterization of wild-type measles viruses in China during 1995-2004 demonstrated that genotype H1 was endemic and widely distributed throughout the country. H1-associated cases and outbreaks caused a resurgence of measles beginning in 2005. A total of 210,094 measles cases and 101 deaths were reported by National Notifiable Diseases Reporting System (NNDRS) and Chinese Measles Laboratory Network (LabNet) from 2006 to 2007, and the incidences of measles were 6.8/100,000 population and 7.2/100,000 population in 2006 and 2007, respectively. Five hundred and sixty-five wild-type measles viruses were isolated from 24 of 31 provinces in mainland China during 2006 and 2007, and all of the wild type virus isolates belonged to cluster 1 of genotype H1. These results indicated that H1-cluster 1 viruses were the predominant viruses circulating in China from 2006 to 2007. This study contributes to previous efforts to generate critical baseline data about circulating wild-type measles viruses in China that will allow molecular epidemiologic studies to help measure the progress made toward China's goal of measles elimination by 2012

Genetic introgression and species boundary of two geographically overlapping pine species revealed by molecular markers.

Gene introgression and hybrid barriers have long been a major focus of studies of geographically overlapping species. Two pine species, Pinus massoniana and P. hwangshanensis, are frequently observed growing adjacent to each other, where they overlap in a narrow hybrid zone. As a consequence, these species constitute an ideal system for studying genetic introgression and reproductive barriers between naturally hybridizing, adjacently distributed species. In this study, we sampled 270 pine trees along an elevation gradient in Anhui Province, China and analyzed these samples using EST-SSR markers. The molecular data revealed that direct gene flow between the two species was fairly low, and that the majority of gene introgression was intermediated by backcrossing. On the basis of empirical observation, the on-site distribution of pines was divided into a P. massoniana zone, a hybrid zone, and a P. hwangshanensis zone. STRUCTURE analysis revealed the existence of a distinct species boundary between the two pine species. The genetic boundary of the hybrid zone, on the other hand, was indistinct owing to intensive backcrossing with parental species. Compared with P. massoniana, P. hwangshanensis was found to backcross with the hybrids more intensively, consistent with the observation that morphological and anatomical characteristics of trees in the contact zone were biased towards P. hwangshanensis. The introgression ability of amplified alleles varied across species, with some being completely blocked from interspecific introgression. Our study has provided a living example to help explain the persistence of adjacently distributed species coexisting with their interfertile hybrids

Genetic parameters associated with each of the 14 EST-SSR primers.

<p>Note: <i>Ho</i>, <i>He, F_ST</i> and <i>Nm</i> are defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101106#s2" target="_blank">Materials and Methods</a>.</p

Bayesian admixture analysis of pines sampled within different elevation intervals.

<p>(<b>a</b>) Box-and-whisker diagram of ln <i>Pr</i>[<i>X</i>/<i>K</i>] for 10 runs at each <i>K</i> and <i>ΔK</i>, based on the rate of change of ln <i>Pr</i>[<i>X</i>/<i>K</i>] between successive <i>K</i> values. (<b>b</b>) Bayesian inference of population structure for <i>K</i> = 2 and <i>K</i> = 3. The elevation range was divided into nine intervals. Each interval contained approximately 30 samples and varied in size from 100 to 200 m depending on tree dispersal. Red, green and blue regions correspond to clusters 1, 2 and 3, respectively.</p

Overview of the Huangshan Mountain sampling strategy.

<p>Note: The transect line (dotted line) started at the town of Tangkou (430 m) and ended at Bright Top Peak (1,820 m).</p

Variation in allele frequencies among different elevation intervals.

<p>(<b>a–i</b>) Genetic loci of different primer pairs. Alleles labeled with a down-arrow are type-II alleles, whose frequencies were negatively correlated with increasing elevation; alleles labeled with an up-arrow represent type-III alleles, whose frequencies were positively correlated with increasing elevation. The elevation range was divided as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101106#pone-0101106-g002" target="_blank">Fig. 2</a>. Only type-II and type-III alleles generated by different primers are displayed; type-I alleles, whose frequencies were uncorrelated with elevation, are not shown.</p

Genetic parameters associated with samples collected from each species zone.

<p>Note: <i>Na</i>, <i>Ne</i>, <i>I</i>, <i>Ho</i>, <i>He</i> and <i>F_IS</i> are defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101106#s2" target="_blank">Materials and Methods</a>.</p

Rubella Virus Genotypes in the People's Republic of China between 1979 and 2007: a Shift in Endemic Viruses during the 2001 Rubella Epidemic▿ †

The incidence of rubella cases in China from 1991 to 2007 was reviewed, and the nucleotide sequences from 123 rubella viruses collected during 1999 to 2007 and 4 viral sequences previously reported from 1979 to 1984 were phylogenetically analyzed. Rubella vaccination was not included in national immunization programs in China before 2007. Changes in endemic viruses were compared with incidences of rubella epidemics. The results showed that rubella epidemics occur approximately every 6 to 8 years (1993/1994, 2001, and 2007), and a shift of disease burden to susceptible young adults was observed. The Chinese rubella virus sequences were categorized into 5 of the 13 rubella virus genotypes, 1a, 1E, 1F, 2A, and 2B; cocirculations of these different genotypes were found in China. In Anhui province, a shift in the predominant genotype from 1F and 2B to 1E coincided with the 2001 rubella epidemic. This shift may have occurred throughout China during 2001 to 2007. This study investigated the genotype distribution of rubella viruses in China over a 28-year period to establish an important genetic baseline in China during its prevaccination era