China has the second largest birth cohort in the world and the second highest number of deaths due to rotavirus infection. It is also the only country with a licensed rotavirus vaccine. Chinese policy makers now need credible estimates of the burden of rotavirus disease, to decide about vaccine use. From August 2001 through July 2003, prospective hospital-based surveillance for rotavirus diarrhea among children <5 years of age was conducted in 6 sentinel hospitals. Rotavirus isolates were characterized to determine the G and P genotypes circulating during the study. Of 3149 children who were admitted to the hospitals for diarrhea and for whom screening for rotavirus was performed, 1590 (50%) had positive results of an antigen detection assay. Of all episodes of rotavirus diarrhea, 95% occurred during the first 2 years of life. The most common rotavirus strain was P[8]G3 (49% of episodes), and all the common strains were detected, including G9 strains (4% of episodes). Ongoing efforts are under way to more precisely define the burden of rotavirus diarrhea in urban and rural populations, to assess the proportion of episodes that may be due to unusual or emerging strains, and to estimate the economic burden of rotavirus disease.

As part of a national rotavirus surveillance activity, we collected fecal specimens from 3,177 children with acute diarrhea in 10 regions of China between April 1998 and April 2000 and screened them for rotavirus. Rotavirus was detected in 41% (n ‫؍‬ 1,305) of specimens, and in these, G1 was the predominant serotype (72.6%), followed by G3 (14.2%), G2 (12.1%), G4 (2.5%), G9 (0.9%), and G untypeable (0.7%). Among 327 G-typed strains tested for P genotype, 14 different P-G combinations were identified, with the globally common strains P [8]G1, P[4]G2, P[8]G3, and P[8]G4 representing 75.6% of all typed rotavirus strains. Among the uncommon strains, 11 were P[6]G9, and others included P[6]G1, P[6]G3, and five novel P-G combinations (P[9]G1, P[4]G1, P[4]G3, P[4]G4, and P[8]G2).Our results indicate that while the common rotavirus strains remain predominant, the diversity of strains is much greater than was previously recognized.

Rotaviruses cause acute diarrhea worldwide. Previous studies of rotavirus diarrhea in China found that rotavirus infection is the most common cause of severe diarrhea in young children. In the present study, surveillance of rotavirus diarrhea was conducted involving 9549 children aged <5 years who were admitted for treatment of diarrhea at 11 sentinel hospitals in China from August 2003 through July 2007. Group A rotavirus was detected in 3749 (47.8%) of the 7846 fecal specimens by using enzyme-linked immunosorbent assay. Rotavirus isolates were characterized by reverse-transcriptase polymerase chain reaction to determine G and P genotypes. All the strains that are common worldwide were detected; G3P[8] was the most common. An unusual G5 strain was detected in 2 specimens. Of all episodes of rotavirus diarrhea, 94% occurred during the first 2 years of life, peaking at 6-23 months of age. Our findings indicate that globally common rotavirus strains continue to be a major cause of severe childhood diarrhea in China. Introduction of routine immunization with effective rotavirus vaccines would substantially reduce this burden.

The incidence of measles in China from 1991 to 2008 was reviewed, and the nucleotide sequences from 1507 measles viruses (MeV) isolated during 1993 to 2008 were phylogenetically analyzed. The results showed that measles epidemics peaked approximately every 3 to 5 years with the range of measles cases detected between 56,850 and 140,048 per year. The Chinese MeV strains represented three genotypes; 1501 H1, 1 H2 and 5 A. Genotype H1 was the predominant genotype throughout China continuously circulating for at least 16 years. Genotype H1 sequences could be divided into two distinct clusters, H1a and H1b. A 4.2% average nucleotide divergence was found between the H1a and H1b clusters, and the nucleotide sequence and predicted amino acid homologies of H1a viruses were 92.3%–100% and 84.7%–100%, H1b were 97.1%–100% and 95.3%–100%, respectively. Viruses from both clusters were distributed throughout China with no apparent geographic restriction and multiple co-circulating lineages were present in many provinces. Cluster H1a and H1b viruses were co-circulating during 1993 to 2005, while no H1b viruses were detected after 2005 and the transmission of that cluster has presumably been interrupted. Analysis of the nucleotide and predicted amino acid changes in the N proteins of H1a and H1b viruses showed no evidence of selective pressure. This study investigated the genotype and cluster distribution of MeV in China over a 16-year period to establish a genetic baseline before MeV elimination in Western Pacific Region (WPR). Continuous and extensive MeV surveillance and the ability to quickly identify imported cases of measles will become more critical as measles elimination goals are achieved in China in the near future. This is the first report that a single endemic genotype of measles virus has been found to be continuously circulating in one country for at least 16 years.

A study was conducted to investigate the circulation of HRSV subgroup B (HRSVB) in China in recent years. HRSVB sequences from 365 samples collected in 1991, 2004 and 2008–2014 in China, together with 332 Chinese HRSVB sequences obtained from GenBank were analyzed to determine the geographic and yearly distribution of HRSVB. Phylogenetic analysis revealed these HRSVB sequences clustered into 4 genotypes with different frequencies: BA (83%), CB1 (11%), SAB (3.0%) and GB3 (0.7%). Between 2005 and 2013, there was a co-circulation of BA and non-BA genotypes in China. Genotypes BA9 and BA10 were two of the main BA genotypes detected in this study. Genotype BA9 was first detected in China in 2006 and became the predominant HRSVB genotype circulating in China from 2008 to 2014. Three different lineages were detected for both genotypes BA9 and BA10. Time to the most recent common ancestor for genotypes BA9 and BA10 was estimated for years 1997 and 1996, respectively. Results of this study not only contribute to the understanding of the circulation pattern, but also the phylogenetic pattern and evolution of HRSVB in China from 1991 to 2014.