Rotavirus is a leading cause of severe acute gastroenteritis in children worldwide, and globally licensed vaccines are available. To expedite the introduction of rotavirus vaccines in the national immunisation programme, a simple, ecological method to monitor changes in the burden of rotavirus disease may be of great help. Here, we report an application of a time-series analysis on a publicly-available dataset in Japan on the weekly number of laboratory-confirmed rotavirus-positive samples over the last 5 year period between the 36th week of 2009 and the 35th week of 2014 during which rotavirus vaccines became marketed in Japan and presumed to reach an uptake rate of at least 39% as a national average. Compared with the expected number of rotavirus detection based on the preceding four rotavirus seasons, the number of rotavirus detection during the 2013–2014 season was 42.9% (95% CI: 38.6, 47.8). This suggests that the use of rotavirus vaccine had a positive impact on reducing the burden of rotavirus diarrhoea in Japan. This method, because of its simplicity and little cost, should be applicable to early detection of the impact of rotavirus vaccine even in resource-poor countries where the World Health Organization funded and implemented the sentinel surveillance programmes of laboratory-confirmed rotavirus cases.

Rotavirus is a leading cause of severe acutegastroenteritis in children worldwide, and globally licensed vaccines areavailable. To expedite the introduction of rotavirus vaccines in the nationalimmunisation programme, a simple, economical method to monitor changes in theburden of rotavirus disease may be of great help. Here, we report anapplication of a time-seriesanalysis on a publicly-available dataset in Japan on the weekly number oflaboratory-confirmed rotavirus-positive samples over the last 5 year period betweenthe 36th week of 2009 and the 35th week of 2014 during which rotavirus vaccines became marketed in Japan andpresumed to reach an uptake rate of at least 39% as a national average. Comparedwith the expected number of rotavirus detection based on the preceding four rotavirusseasons, the number of rotavirus detection during the 2013-2014 season was 43%(95% CI: 38.6, 47.8). This suggeststhat the use of rotavirus vaccine had a positive impact on reducing the burdenof rotavirus diarrhoea in Japan. This method, because of its simplicity andlittle cost, should be applicable to early detection of the impact of rotavirusvaccine even in resource-poor countries where the World Health Organizationfunded and implemented the sentinel surveillance programmes oflaboratory-confirmed rotavirus cases.

Rotavirus A causes severe diarrhoea in infants and young children worldwide. Many unusual combinations of G and P genotypes have been observed in rotaviruses circulating in developing countries. Mixed infection of a single individual with more than one strain is a mechanism by which genetic reassortants are formed with unusual G and P combinations. However, few studies have provided direct evidence for the formation of such unusual strains as a result of co-infection of co-circulating strains. Here, we used full-genome sequencing to re-analyze a G3P[4] strain (107E1B) and a G2P[4] strain (116E3D) detected in India in 1993 and showed that 107E1B had virtually an identical nucleotide sequence with 116E3D, except the VP7 gene. Phylogenetic analysis revealed that the 107E1B VP7 gene was of typical human rotavirus origin, with a 99.3% nucleotide sequence identity with another Indian G3 VP7 gene. Thus, this study provided robust evidence for the formation of the G3P[4] strain through genetic reassortment in which a G2P[4] strain with a typical DS-1 genogroup background acquired the VP7 gene from a co-circulating G3 human rotavirus strain. This study established a basis on which to facilitate full genome sequence analysis of an increasing number of G3P[4] strains in China and elsewhere in the world.

Rotavirus A causes severe diarrhoea in infants and young children worldwide. The migration pattern (electropherotype) of the double-stranded RNA genome upon polyacrylamide gel electrophoresis has been used to define “strains” in molecular epidemiology. In temperate countries, distinct electropherotypes (strains) appear after the annual, off-seasonal interruption of rotavirus circulation. In Nepal, rotavirus circulated year-round and an uncommon genotype G12P[6] predominated and persisted, providing a unique opportunity to examine whether the same electropherotype (the same strain) persisted or new electropherotypes (new strains) emerged successively under the same G12P[6] predominance. A total of 147 G12P[6] rotaviruses, collected from diarrhoeal children in Nepal between 2007 and 2010, were classified into 15 distinct electropherotypes (strains). Of these, three electropherotypes (strains), LP1, LP24, and LP27, accounted for 10%, 32% and 38% of the G12P[6] rotaviruses, respectively. Each of the three major strains successively appeared, dominated, and disappeared. This study provided new evidence for the hypothesis that rotavirus constantly changes its strains to predominate in the local population even under conditions where a single genotype predominates and persists. Such dynamic strain replacement, the constant takeover of one predominant strain by another, fitter strain, is probably gives a competitive edge to the survival of rotavirus in nature.

Rotavirus B (RVB) in the genus Rotavirus of the family Reoviridae is known to be a cause of acute gastroenteritis among children and adults in parts of Asia including China, India, Bangladesh and Myanmar. In a 15-month surveillance programme between March 2007 and May 2008, 3,080 stool specimens were collected from children and adults with acute gastroenteritis in an infectious disease hospital in Kathmandu, Nepal. In 25 (0.8%) specimens RVB was detected, for the first time in Nepal, by the use of polyacrylamide gel electrophoresis followed by confirmation with reverse-transcription PCR and sequencing. The strains detected in this study had very similar electropherotypes, and their VP7 sequences were almost identical and phylogenetically belonged to the Indo-Bangladeshi lineage which was distinct from the Chinese lineage. Thus, this study showed the circulation of RVB strains belonging to the Indo-Bangladeshi lineage in a broader region than previously documented, suggesting that this phylogenetic divide corresponded to the geographic divide created by the Himalayan Mountains. Further studies may be warranted to identify and characterize the RVB strains in northern Vietnam which is adjacent to southern China with a long and less mountainous border.