Emergence of serotype G9 human rotaviruses in Australia

Molecular Characterization of Human Rotavirus from Children with Diarrhoeal Disease in Sokoto State, Nigeria

This study was conducted to detect and characterize prevalent human group A rotavirus strains from 200 diarrheic children in Sokoto, Nigeria, by ELISA, monoclonal antibody (Mab) serotyping and Reverse Transcription-Polymerase Chain Reaction (RT-PCR) techniques. Rotavirus was detected in 25.5% of the children. The G-serotypes observed in circulation were G4: 16 (59.3%), G1: 4 (14.8%), G2: 3 (11.1%), G3: 3 (11.1%), and G12: 1 (3.7%). The monoclonal antibody (Mab) serotyping detected G1 and G3 but did not detect G4 and G2 serotypes. The Mab typing of the G1 and G3 serotypes was consistent with the result of the RT-PCR. The VP4 genotypes detected were P[6] 3 (13%), P[8] 11 (47.8%), and the rare human P genotype (P[9]), found in 9 patients (39.1%). Nine strains identified with the common G and P combinations were G4 P[8] 5 (56%), G4 P[6] 1 (11%), G1 P[8] 2 (22%), and G3 P[8] 1 (11%), while seven strains with unusual combinations or rare G or P genotypes identified were G12 P[8] 1 (14%), G2 P[8] 2 (29%), and G4 P[9] 4 (57%). To our knowledge this is the first molecular study of human rotavirus and report of rare human G and P serotypes in Sokoto State.

Characterisation of a G9P[8] rotavirus strain identified during a gastroenteritis outbreak in Alice Springs, Australia post Rotarix™ vaccine introduction

A large rotavirus gastroenteritis outbreak occurred in the Alice Springs region of the Northern Territory, Australia from the 12th of March until the 11th of July 2007. The outbreak occurred five months after the introduction of the Rotarix™ vaccine. Electropherotype and sequence analysis demonstrated that a single G9P[8] strain was responsible for the outbreak and that the strain remained highly conserved during the outbreak period. The outbreak strain contained amino acid changes in regions of the VP7 and NSP4 genes, with known biological function, when compared to previously characterised G9P[8] strains from Australia and other international locations. The recent vaccine introduction was unlikely to have influenced genotype selection in this setting. Importantly, Rotarix™ vaccine was highly effective against the G9P[8] outbreak strain.

Circulating human group A rotavirus genotypes in Malaysia

This study examined the temporal distribution of rotavirus genotypes in Malaysia. Rotaviruses from children with diarrhea admitted to hospitals in 1996 (n = 93) and 2007 (n = 12) in two different regions of Peninsular (West) Malaysia were analyzed for their G and P genotypes using a hemi-nested RT-PCR assay. In the 2007 samples, the dominant strain was G9P[8]. It was identified in 42% of the samples. Different strains all possessing the G1 genotype were identified in the rest of the samples. In contrast, 81% of the samples collected in 1996 were the G1P[8] strain. No strains with G9 genotype were detected in samples collected in 1996.

Emergence of G12 rotavirus strains in Delhi, India, in 2000 to 2007

The prospect that rotavirus diarrhea in children may soon be prevented by vaccines has placed a new priority on understanding the diversity of rotavirus strains and the mechanism by which these strains evolve over time. We have characterized a total of 465 rotavirus strains collected in North India from 2000 to 2007 for G and P types by reverse transcription-PCR and sequencing. The novel G12 rotavirus strains recently detected in other countries were first detected in India in 2001 and have emerged as the predominant strains in Delhi, India, during 2005 to 2007. While the VP7 sequence was highly homologous among G12 strains isolated in Delhi, suggesting recent emergence from a common ancestor, the strains had a diverse constellation of other gene segments, demonstrating substantial reassortment. For the entire period, the common rotavirus G types G1 (26%), G2 (25%), and G9 (14%) comprised 65% of the strains, and common P types, P[4] (19%), P[6] (22%), and P[8] (35%), comprised 76% of the total P types. Of note, we detected a high percentage of unusual (17%) strains and fecal specimens with mixed (12% G and 15% P) rotavirus infections having a variety of genomic constellations. For the first time, we identified two novel rotavirus strains with unusual G/P combinations, G2P[11] and G3P[11], in patients with diarrhea. The study highlights the great diversity among rotaviruses isolated from Indian children, the opportunity for genetic reassortment between strains, and the emergence of a novel G12 strain in our country. Due to the demonstrated effect of antigenic diversity on rotavirus vaccines, it will be important to continue careful monitoring of these strains as rotavirus vaccine programs are implemented in India.

G and P rotavirus genotypes in stool samples from children in Teresina, State of Piauí

A total of 123 stool specimens collected in Teresina, Piauí between 1994 and 1996, from 0 to 2-year-old children with diarrhea, were used for this study. Molecular characterization of the G and P rotavirus genotypes was performed using the reverse transcriptase polymerase chain reaction. The following results were obtained for the P genotypes: P[8] (17. 1%), P[1] (4. 9%), P[4] (3. 3%), P[6, M37] (2. 4%) and mixtures (27. 6%). The P[1]+P[8] mixture was found in 19. 5% of the samples. For the G genotypes, the results were: G1 (25. 2%), G5 (13. 8%), G2 (2. 5%), G4 (2. 5%), G9 (0. 8%) and mixtures (41. 5%). G1+G5 was the mixture most frequently found (12. 1%). Our results showed unusual combinations such as P[1]G5 and P[1]+P[8]G5. The high percentage of mixtures and unusual combinations containing mixtures of human and animal rotavirus genotypes strongly suggests the possibility of gene reassortment and interspecies transmission.

Genetic distribution of group A human rotavirus types isolated in Gyunggi province of Korea, 1999–2002

BACKGROUND

Human rotavirus genotypes G1-G4 and G9 are the major etiological agents of infantile gastroenteritis. G1 was the most prevalent in Korea during the 10-year period prior to 1997. However, between 1998 and 1999, G4 was the predominant type in Korea, as it was in other Asian countries.

OBJECTIVES

The circulating pattern and genetic variability of group A human rotavirus in Gyunggi, Korea, 1999-2002, were examined in 189 stool specimens.

STUDY DESIGN

Stool samples were collected from children with diarrhea, and group A human rotavirus type was determined using multiplex RT-PCR in those specimens found to be positive for rotavirus by ELISA. Each genotype was sequenced, and phylogenetic analysis was performed on the sequences.

RESULT

We found significant variability from year to year in the prevalence of different G and P types of rotavirus. We also found relatively high prevalence rates for types normally considered to be uncommon. Furthermore, we found that the most prevalent combination of G and P types changed from year to year. Although the combination of G and P types changed every year, the sequence of G genotypes showed a high level of similarity (>97%) compared to those of strains from other Asian countries.

CONCLUSION

We report the types of rotavirus circulating in Gyunggi province, Korea from 1999 to 2002. This information on rotavirus diversity has important implications for rotavirus vaccine efficacy and future vaccine development.

Association of the G4 rotavirus genotype with gastroenteritis in adults

Rotavirus is the most common etiological cause of acute viral gastroenteritis in infants and young children worldwide, yet its role in the adult population is less well understood. We have recently identified rotavirus as the causative agent of severe diarrhea in adults, specifically in two gastroenteritis outbreaks in separate care for the elderly homes. Strain typing has shown the continued presence of P[8]G1, the emergence of P[8]G9, and the reemergence of P[8]G4. A total of 26 community cases and 6 outbreak cases of rotavirus infection, positive via a molecular screening assay, were subsequently amplified using VP4 and VP7 specific primers (Con2/Con3 and 1A/1B primer sets, respectively). The age range of patients investigated was from <1 year to 89 years. The resulting PCR products were cloned into TOPO10 PCR IV vector and sequenced to give the P- and G-type accordingly. All sequence data were subjected to BLAST analysis. Three different rotavirus types P[8]G1, P[8]G4, and P[8]G9 were identified. Types P[8]G1 and P[8]G9 were identified as circulating within the community, whereas the third type P[8]G4 was identified only in an elderly care outbreak. The identification of G9 rotaviruses supports evidence of emergence of the genotype on a global scale.

Genetic variation ofNSP1 andNSP4 genes among serotype G9 rotaviruses causing hospitalization of children in Melbourne, Australia, 1997–2002

Serotype G9 rotaviruses have emerged as one of the leading causes of gastroenteritis in children worldwide. We examined 29 representative G9 rotavirus isolates from a 6-year collection (1997-2002) and determined the level of variation in genes encoding non-structural proteins, NSP1 and NSP4. Northern hybridization analysis with a whole genome probe derived from the prototype G9 strain, F45, revealed that the NSP1 gene (gene 5) of two isolates (R1 and R14) did not exhibit significant homology. Complementary DNA probes of R1 and R14 genes 5 were used in Northern blot hybridization and indicated the presence of at least two gene 5 alleles among Melbourne G9 rotaviruses. Nucleotide sequence analysis revealed that isolates carrying the R14 gene 5 shared 94-98% sequence identities with one another, while sequence identity to R1 was 78%. Surprisingly, R1 displayed 96% nucleotide identity with the prototype serotype G1 strain, Wa. The detection of different alleles of NSP1 genes prompted us to investigate the level of variation in another non-structural protein, NSP4, a multifunctional protein and the first viral-encoded enterotoxin. Phylogenetic analysis indicated that while all isolates clustered into one group containing the Wa NSP4 allele (genotype 1), isolate R1 was most closely related to Wa. This study reveals new information about the diversity of non-structural proteins of G9 rotaviruses.

Detection of group a human rotavirus G9 genotype circulating in Córdoba, Argentina, as early as 1980

The incidence of human rotavirus G types was determined over a 25-year period (1979-2003) by using reverse transcription-PCR (RT-PCR) to examine 519 stool specimens found to be positive for rotavirus by enzyme linked immunosorbent assay (ELISA) or polyacrylamide gel electrophoresis (PAGE). These stool samples were obtained from children under 3 years old who had been treated for acute diarrhea at public hospitals in Córdoba, Argentina. The present study describes the continued circulation of the common human G types G1 (53.8%), G2 (10.2%), G3 (4.4%), and G4 (27%), and also the detection of the unusual types G8 (0.5%) and G9 (4.2%). Genotype G9 was detected during the 1980-1988 and 1997-2003 periods at relatively low rates. Rotavirus G types distribution was independent of age (1-18 months), gender or out-patient or in-patient status. Unexpectedly, 44.6% of mixed infections were detected, involving common and unusual genotypes. Overall, 95.4% of the typed strains belonged to the most prevalent human serotypes (G1-G4) but the detection of G9 infection throughout this study period highlights the importance of this serotype as a human pathogen.

Predominance of rotavirus G9 genotype in children hospitalized for rotavirus gastroenteritis in Belgium during 1999–2003

BACKGROUND

Group A rotavirus genotypes G1, G2, G3 and G4 are the main etiological agents of infantile diarrhea. The G9 rotavirus has recently emerged as a fifth important genotype all over the world.

OBJECTIVE

To characterize the VP7 gene of group A rotaviruses from gastroenteritis patients admitted to the Gasthuisberg University Hospital, Leuven, Belgium, during 1999-2003.

STUDY DESIGN

Rotavirus antigen was detected in stool specimens using an enzyme immunoassay. G-typing was performed by reverse transcriptase polymerase chain reaction (RT-PCR) amplification and sequencing of the complete VP7 gene.

RESULTS

The genotype distribution varied markedly over the four rotavirus years in Belgium. In the 1999-2000 rotavirus year, G1 was the predominating type (72%), and G9 was present in 5% of the rotavirus-positive patients. In the 2000-2001 and 2002-2003 years, G9 appeared as the dominating strain (45% and 53%, respectively). In the 2001-2002 year, between two G9 epidemic years, G1 was dominating (66%) but G9 was still present in 24%. All the G9 isolates were combined with P[8] and shared a high gene sequence similarity (<3% sequence divergence on the nucleotide and amino acid level). Phylogenetic analysis of the VP7 genes revealed that our Belgian G9 strains clustered together with recent G9 strains from all over the world, distinct from the prototype G9 strains isolated in the 1980s.

CONCLUSION

Our study indicates that although the first introduction of G9 isolates in the Belgian population was recorded in 1997, G9 strains were able to establish themselves quickly as the predominant genotype. The emergence of G9 as an important pathogen in both developing as industrialized countries necessitates the urgent consideration of the G9 moiety in rotavirus vaccines.

Phylogenetic analyses of human rotavirus in central Taiwan in 1996, 2001 and 2002

BACKGROUND

Rotavirus epidemiology information is required for gastroenteritis disease control and prevention. Information gathered about the serotype distribution of rotaviruses isolated in Taiwan is of crucial significance, before a licensed rotavirus vaccine is introduced.

OBJECTIVES

The purpose of the present study is to investigate the epidemiological diversity of rotaviruses in Taiwan.

STUDY DESIGN

A total of 51 stool samples taken from cases of acute gastroenteritis were collected from three teaching hospitals in central Taiwan in 1996, 2001 and 2002. The samples were subjected to RT-PCR tests of VP7 gene of the human rotavirus group A, B, C.

RESULTS

A total of 16 stool samples were detected positive by RT-PCR and 10 were sequence analyzed and classified into G1, G3, and G9 types. Compared with other HRV strains: the sequences of CS96-40 of G1 are similar to MVD9816 (identity rate 97.15% and 96.09%, respectively, from Uruguay); the sequences of CS02-01 of G3 are similar to 98-B31 (identity rate 98.93% and 98.72%, respectively, from Japan); the sequences of CS01-05, CS01-06, CS01-07, CS01-09, CS01-13, CS02-02, CS02-03, CS02-04 are very similar to other established G9 rotaviruses sequences (identity rate 96.85-99.88%), especially between CS02-04 and SP2737 (from Japan) with an identity rate of 99.88% and 100% nucleotide and amino acid, respectively. Except for CS01-06 strain, it is VR3, but not VR5, VR7 or VR8, that found to be the most frequent mutated amino acid regions of VP7 in these strains.

CONCLUSIONS

Our findings are the first to document the high prevalence of G9 HRV strains in Taiwan, and suggest the re-emergence of G3 strains in central Taiwan since 1991. Epidemiological surveys carried out in this study suggest genotype shifts from type G1 before 1996, to G9 in 2001 and 2002 and the re-emergence of G3 type in 2002.

Global distribution of rotavirus serotypes/genotypes and its implication for the development and implementation of an effective rotavirus vaccine

A safe and effective rotavirus vaccine is urgently needed, particularly in developing countries. Critical to vaccine development and implementation is a knowledge base concerning the epidemiology of rotavirus G and P serotypes/genotypes throughout the world. The temporal and geographical distribution of human rotavirus G and P types was reviewed by analysing a total of 45571 strains collected globally from 124 studies reported from 52 countries on five continents published between 1989 and 2004. Four common G types (G1, G2, G3 and G4) in conjunction with P[8] or P[4] represented over 88% of the strains analysed worldwide. In addition, serotype G9 viruses associated with P[8] or P[6] were shown to have emerged as the fourth globally important G type with the relative frequency of 4.1%. When the global G and/or P type distributions were divided into five continents/subcontinents, several characteristic features emerged. For example, the P[8]G1 represented over 70% of rotavirus infections in North America, Europe and Australia, but only about 30% of the infections in South America and Asia, and 23% in Africa. In addition, in Africa (i) the relative frequency of G8 was as high as that of the globally common G3 or G4, (ii) P[6] represented almost one-third of all P types identified and (iii) 27% of the infections were associated with rotavirus strains bearing unusual combinations such as P[6]G8 or P[4]G8. Furthermore, in South America, uncommon G5 virus appeared to increase its epidemiological importance among children with diarrhea. Such findings have (i) confirmed the importance of continued active rotavirus strain surveillance in a variety of geographical settings and (ii) provided important considerations for the development and implementation of an effective rotavirus vaccine (e.g. a geographical P-G type adjustment in the formulation of next generation multivalent vaccines).

Rotavirus serotype G9P[8] and acute gastroenteritis outbreak in children, Northern Australia

Amino acid substitutions on the VP7 and NSP4 proteins were identified in regions known to influence function and may have contributed to the emergence and increased dominance of the outbreak strains.

During 2001, an outbreak of severe acute gastroenteritis swept through Central and northern Australia and caused serious disruption to health services. We tracked and characterized the rotavirus strain implicated in the outbreak. Comparison of the electropherotypes of outbreak samples suggested that one G9P[8] strain was likely responsible for the outbreak. Samples were obtained from geographically distinct regions of Australia where the epidemic had occurred. The outbreak strains showed identical nucleotide sequences in genes encoding three rotavirus proteins, VP7, VP8, and NSP4, but they were distinct from G9P[8] strains isolated in previous years. Several of the amino acid substitutions on the VP7 and NSP4 proteins were identified in regions known to influence function and may have contributed to the emergence and increased dominance of the outbreak strains. Rotavirus serotype surveillance should continue with methods capable of identifying new and emerging types.

Evidence of rotavirus AU32 like G9 strains from nontypeable fecal specimens of Indian children hospitalized during 1993-1994

Serotyping of 432 rotavirus positive fecal specimens collected from hospitalized children during 1990-1997 was carried out at National Institute of Virology (NIV), Pune, India, using monoclonal antibodies (MAbs) directed against VP7 determinant of serotypes G1-G4, G6, G8, and G10. However, significant number of specimens, that is, 47.92% remained nontypeable. The aim of the present study was to culture adapt the nontypeable specimens and to characterize them further. Since the fecal specimens were not tested by MAb to G9 serotype, which has emerged as an important serotype infecting humans recently, presence of G9 serotype was expected in nontypeable specimens. Therefore, we selected specimens from those children, who showed higher neutralizing antibody (NAb) titer in their convalescent serum samples to G9 serotype than their mothers. Out of six isolates having long electropherotype, five isolates showed subgroup II, and one showed subgroup I, II. The isolates were confirmed as G9 by MAb based ELISA, neutralization assay, and PCR. The G9 specific nested PCR products of four isolates showed 96-99% identities to AU32 G9 strain reported from Japan. P type of four isolates was determined as P8. Besides isolates, four additional nontypeable fecal specimens were confirmed as G9 by MAb based ELISA. Thus, 10 (28.57%) out of 35 nontypeable specimens were identified as rotavirus serotype G9. The results indicate that serotype G9 may represent significant proportion of specimens, which were previously nontypeable.

Diversity of group A human rotavirus types circulating over a 4-year period in Madrid, Spain

The incidence and distribution of human rotavirus G types among children under 5 years old with acute gastroenteritis were determined over a 4-year period (1998 to 2002) by using monoclonal antibodies and reverse transcription-PCR methods. Rotavirus was detected in 1,155 (31%) of 3,760 specimens tested. Rotavirus was studied in every month of the 48-month survey period. Rotavirus activity occurred mainly (51%) in the typically cooler months in Spain (November to February). The age distribution of rotavirus-positive cases showed that 90% of patients (1,038 of 1,155) were under 2 years old. Rotavirus types were determined for 576 of 1,155 patients (50%). G1 was the main genotype detected (53%), and the second most common was G4 (24%). The G2, G9, and G3 rotavirus types were detected in 14, 6, and 2% of the cases, respectively. Dual infections were detected in only 0.6%. The seasonal distribution of genotypes showed a significant genotypic shift: whereas G4 strains predominated (57%) during the 1998 to 2000 seasons, the G1 gradually increased to account for 75% in the 2000 to 2002 seasons. In addition, the present study reports the first detection of the G9 genotype in human fecal samples in Spain. Therefore, additional types may be required for vaccine development strategies that currently target only types G1 to G4.

Eight-year survey of human rotavirus strains demonstrates circulation of unusual G and P types in Hungary

Between 1992 and 2000, a total of 4173 rotavirus-positive samples were collected from two areas of Hungary. Of these, 2020 specimens (48.4%) were analyzed for G serotype, using monoclonal antibody-based immunoassay and reverse transcription-PCR. By the two methods, 1789 samples were specified as G1 (62%), G2 (12.2%), G3 (1.4%), G4 (6.4%), G6 (1.0%), G9 (2.9%), or mixed infection (2.6%), and the remaining 231 (11.4%) could not be G typed. The linkage between G and P type, subgroup specificity, and RNA profile was investigated with a sample subset. Among these specimens, we identified both the four globally common strains (P[8],G1 subgroup II (sgII); P[4],G2 sgI; P[8],G3 sgII; and P[8],G4 sgII) and six uncommon strains (P[6],G4 sgII; P[9],G3 sgI; P[9],G6 sgI; P[14],G6 sgI; P[8],G9 sgII; and P[8],G9 sgI). All strains with P[8], P[6], P[9], and P[14] specificities had a long electropherotype, whereas most of those carrying a P[4] specificity were associated with a short electropherotype. Although once considered to be rare, P[9],G6 and P[8],G9 rotavirus strains represent potentially important new serotypes in Hungary.

Serologic and genomic characterization of a G12 human rotavirus in Thailand

The G and P type specificity of the human rotavirus strain T-152 (G12P[9]) isolated in Thailand was serologically confirmed with G12-specific monoclonal antibodies prepared in this study by using a reference G12 strain, L26, as an immunizing antigen and a P[9]-specific monoclonal antibody, respectively. The genomic relationship of strain T-152 with representative human rotavirus strains was examined by means of Northern blot analysis. The results showed that T152 is closely related to strain AU-1 (G3P[9]). Gene 5 (NSP1 gene) of T152, which did not hybridize with those of any other strains examined, was characterized by sequence determination. The T152 NSP1 gene is 1,652 nucleotides in length, encodes 493 amino acids, and exhibits low identity to those of representative human and animal rotaviruses.

Genetic variability of human rotavirus strains isolated from Eastern and Northern India

An epidemiological study was conducted in Eastern and Northern India to determine the genomic diversity of rotaviruses in these parts of the country. In 2001, a total of 126 Group A rotavirus positive samples were detected from children below 4 years of age with diarrhoea from Kolkata, Dibrugarh and Bhubaneswar in Eastern India, and Chandigarh, a city in Northern India. All the samples were genotyped for VP7 (G-type) and VP4 (P-type) gene by reverse transcription (RT) and multiplex PCR using different type specific primers. The strains with G1P[8] (32.5%) was predominant as reported earlier [Das et al. (2002) J Clin Microbiol 40:146-149] followed by G2P[4](4.7%) and only one sample was of G4P[8] specificity. Along with these common types some rare strains like G1P[6], G2P[8], G2P[6], G4P[4], and G4P[6] were also detected in 14.3% of cases. Thirty percent of samples in this study were mixed infections and 21 (16.7%) specimens remained untypeable either for the VP7 or for the VP4 gene. After sequencing of the VP7 gene, two G9 strains (RMC321 and ISO-3) were identified with P[8] and P[19] specificities. Sequence analysis revealed that they have much lower homology to the G9 strains (116E, INL1, and G16) isolated earlier from Indian subcontinent, but have much higher homology to isolates from Argentina, Brazil, Malawi, Taiwan, and USA suggesting a separate progenitor for these strains.

Nucleotide variation in the VP7 gene affects PCR genotyping of G9 rotaviruses identified in Italy

A modified (aFT9m) and a degenerate (aFT9d) version of the rotavirus G9-specific primer (aFT9) allowed strains that were previously untypable, because of point mutations accumulating at the primer binding site, to be G typed by reverse transcription-polymerase chain reaction. The strains were collected during 2001-2002 in Italy in hospitals of the Apulia region, from children affected by severe rotavirus-associated enteritis. Using a wide selection of G9 rotaviruses detected worldwide, sequencing of the G9 untypable strains, sequence comparison, and phylogenetic analysis showed that the Italian strains have strong genetic similarity (< or =99.4%) to G9 rotaviruses identified recently in many parts of the world and different from the old G9 strains identified during the 1980s (less than 90%). Genetic variation of G9 rotaviruses explains the constraints encountered in the typing assays and presumably accounts, together with genetic reassortment events, for the emergence on a global scale of the G9 serotype.

Genetic variability among serotype G6 human rotaviruses: identification of a novel lineage isolated in Hungary

Rotavirus serotype G6 has been demonstrated to be a rare cause of gastroenteritis in man. To date, only a few well characterized strains have been described from Italy, Australia, and the United States. Nucleotide sequencing of G6 VP7 genes shows that these strains belong to two distinct G6 lineages, one for strains of serotype P11[14],G6 (PA169-like strains) and one for strains of serotype P3[9],G6 (PA151-like strains). In this study, we sequenced the VP7 genes and VP8* gene fragments of human rotavirus G6 strains detected in Hungary. Phylogenetic analysis demonstrated that the VP7 genes of Hungarian G6 strains fell into three lineages, represented by a single PA169-like strain, three PA151-like strains, and two novel G6 strains, respectively. The amino acid sequence identity of VP7 was 97.2-100% within each lineage and 92-93.9% between any two lineages. The sequence analysis of VP8* revealed that the single PA169-like Hungarian G6 strain belonged to genotype P[14] and was phylogenetically closely related to P11[14],G6 strains characterized previously. In contrast, the VP8* of PA151-like Hungarian G6 strains clustered in accordance with their VP7 genes representing genetically distinguishable variants of genotype P[9]. This finding raises the possibility that Hungarian genotype P[9],G6 strains might have been generated through independent reassortment events. Serotype G6-specific primers for each human G6 lineage were also developed. The use of these primers in reverse-transcription polymerase chain reaction genotyping may help determine the epidemiological role of G6 strains in humans.

Genetic and antigenic characterization of rotavirus serotype G9 strains isolated in Australia between 1997 and 2001

Rotavirus serotype G9 is recognized as the most widespread of the emerging serotypes, emerging since 1996 as a frequent cause of severe acute gastroenteritis in children from many countries covering all continents of the world. This study characterized serotype G9 strains collected in three widely separated Australian centers from 1997 to 2001. All G9 strains possessed the VP4 P[8] and VP6 subgroup II genes. The overall prevalence of the G9 strains increased in Australia, from 0.6% of the strains found in 1997 to 29% of the strains found in 2001. The prevalence of G9 relative to all other serotypes varied from year to year and with geographic location. In Melbourne (representing east coast urban centers), G9 made up 11 to 26% of all of the strains found from 1999 to 2001. In Perth (representing west coast urban centers), G9 made up less than 2% of the strains found in 1997 to 2000 but increased to 18.6% of the strains found in 2001. In Alice Springs (representing widely dispersed settlements in northern arid regions), G9 made up 0 to 5% of the strains found from 1997 to 2000 and was the dominant strain in 2001, making up 68.9% of all of the strains found. Three distinct antigenic groups based on reaction with neutralizing monoclonal antibodies (N-MAbs) were identified, including a dominant group (63%) that cross-reacted with the serotype G4 N-MAb. Phylogenetic analysis of the VP7-encoding gene from Australian strains, compared with a worldwide collection of G9 strains, showed that the Australian G9 strains made up a genetic group distinct from other serotype G9 strains identified in the United States and Africa. Future epidemiological studies of the occurrence of G9 strains should combine reverse transcription-PCR and typing with G1 to G4 and G9 N-MAbs to determine the extent of G9 and G4 cross-reactions among rotavirus strains, in order to assess the need to incorporate G9 strains into new candidate vaccines.

Detection of the emerging rotavirus G9 serotype at high frequency in Italy

Group A human rotavirus strains belonging to the unusual serotype G9 were detected at high frequency in stool specimens from infected children with acute diarrhea in Bari, Italy, during a 15-month survey from March 2001 to June 2002. This may signify a local reemergence of the G9 rotaviruses detected in Italy in the early and mid-1990s or may be related to the global emergence of G9 rotaviruses in recent years.

Characterization of serotype G9 rotavirus strains isolated in the United States and India from 1993 to 2001

The emergence of rotavirus serotype G9 as a possible fifth globally common serotype in the last decade, together with its increasing detection in association with various genome constellations, raises questions about the origins and epidemiological importance of recent G9 isolates. We examined a collection of 40 G9 strains isolated in the United States from 1996 to 2001 and in India since 1993 to determine their VP7 gene sequences, P types, E types, subgroup specificities, and RNA-RNA hybridization profiles. With the exception of two U.S. strains, all of the study strains shared high VP7 gene sequence homology (<2.5% sequence divergence on both the nucleotide and amino acid levels) and were more closely related to other recent isolates than to the first G9 strains isolated in the 1980s. The VP7 gene sequence and RNA-RNA hybridization profiles of the long-E-type strains showed greater variation than the short-E-type strains, suggesting that the latter strains are the result of a relatively recent reassortment event of the G9 VP7 gene into a short-E-type lineage. No evidence for reassortment of genes other than VP4 and VP7 between major human rotavirus genogroups was observed. Except for Om46 and Om67, which formed a distinct clade, phylogenetic analysis showed that most of the study strains grouped together, with some subgroups forming according to genetic constellation, geographic location, and date of isolation. The high potential of G9 strains to generate different P and G serotype combinations through reassortment suggests that it will be important to determine if current vaccines provide heterotypic protection against these strains and underscores the need for continued surveillance for G9 and other unusual or emerging rotavirus strains.

Surveillance of rotavirus strains in Rio de Janeiro, Brazil, from 1997 to 1999

One hundred fifty-seven (23%; n = 678) rotavirus-positive stool samples were collected between March 1997 and December 1999 in the cites of Rio de Janeiro and Niterói. Rotaviruses in 143 (91%) samples were genotyped by reverse transcription-PCR for G and/or P specificity. Rotaviruses in the majority of G-P-typeable samples (73.3%; 74 of 101) were identified as having globally common genotypes G1P[8], G2P[4], G3P[8], and G4P[8]. Unusual strains such as G1P[9], G2[P8], G3P[9], and G9P[4] strains were detected in 8.9% (9 of 101) of the samples. Genotypes G9P[8], G9P[6], and a mixture of G9 and other G or P types represented 15.9% (25 of 157) of the isolates. Mixed infections were detected in 25 (15.9%) samples, and rotaviruses in 15 samples (9.6%) were not typed.

Construction and characterization of rhesus monkey rotavirus (MMU18006)- or bovine rotavirus (UK)-based serotype G5, G8, G9 or G10 single VP7 gene substitution reassortant candidate vaccines

Group A rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide and have been estimated to be responsible for approximately 650,000-800,000 deaths annually in children <5-year-old in the developing countries. Thus, the development of a safe and effective rotavirus vaccine has been a global public health goal. Epidemiologic surveillance of rotavirus VP7 (G) serotypes-genotypes conducted in various populations throughout the world has repeatedly shown that approximately 90% of the typeable rotavirus isolates belong to G1-G4. For these reasons, we have developed a rhesus rotavirus (RRV)-based or bovine rotavirus (UK)-based quadrivalent vaccine which is designed to provide antigenic coverage for G1-G4. More recently, G serotypes-genotypes other than G1-G4, including G5, G8-G10, have been detected in various parts of the world. Although the occurrence of such uncommon G types, except for G9, has been focal, still, in order to "be ready and prepared", we have constructed and characterized eight additional reassortant rotavirus vaccines, each of which bears a single human or bovine VP7 gene encoding G serotype 5, 8, 9 or 10 specificity and the remaining 10 genes of RRV strain MMU18006 or bovine rotavirus strain UK. These candidate vaccines could be evaluated singly in special populations or in combination with a RRV- or an UK-based quadrivalent vaccine to broaden its G serotype specificity.

VP7 gene polymorphism of serotype G9 rotavirus strains and its impact on G genotype determination by PCR

Rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide. Surveillance of rotavirus serotypes/genotypes (both VP7[G] and VP4[P]) is in progress globally in which polymerase chain reaction (PCR) has been the assay of choice. We investigated polymorphism of the VP7 gene of serotype G9 rotavirus strains and its impact on the determination of VP7 gene genotype by PCR assay. By VP7 gene sequence analysis, we and others have previously shown that the G9 rotavirus strains belong to one of three VP7 gene lineages. By PCR assay using three different sets of commonly used primers specific for G1-4, 8 and 9, 23 Brazilian G9 strains and 5 well-characterized prototype G9 strains which collectively represented all three VP7 gene lineages were typed as: (i) G3; (ii) G4; (iii) G9; (iv) G3 and G9; or (v) G9 and G4 depending on a primer pool employed. This phenomenon appeared to be due to: (i) a VP7 gene lineage-specific polymorphism, more specifically mutation(s) in the primer binding region of the VP7 gene of G9 strain; and (ii) the magnitude of difference in nucleotide homology at respective primer binding site between homotypic (G9) and heterotypic (G3 or G4) primers present in a primer pool employed.

Epidemiological features of rotavirus infection among hospitalized children with gastroenteristis in Ho Chi Minh City, Vietnam

An epidemiological study of the G serotype and P genotype distribution of group A rotaviruses by using ELISA and/or RT-PCR was conducted in children (aged 1 month to 15 years) with diarrhea that were admitted to the General Children's Hospital No. 1, Ho Chi Minh City, Vietnam from December 1999 to November 2000. The results showed that rotavirus is associated with 65.6% (889/1355) of diarrheal admissions. Rotavirus infection mostly affected children under 2 years of age with a peak incidence in children 1 to 2 years of age (75.7%) and it occurs year round with a slight seasonal pattern; 99.5% of the specimens could be G-typed: G1 was predominant (68.7%), followed by G4 (15.4%), G2 (12.3%), G3 (0.6%), and G9 (0.5%). High identities of VP7 nucleotide (96.3 to 96.9%) and deduced amino acid (98.1 to 98.4%) were found between two Vietnamese G9 strains and also the recent emergence of G9 strains US 1205, Brazilian R143, and Malawian MW69. Mixed infections were identified in 17 (2.0%), and 5 strains (0.5%) remained untypable. The four most common worldwide strains, G1P[8], G2P[4], G3P[8], and G4P[8], constituted 81.1% of all rotaviruses typed with G1P[8] being the most prevalent type (58.2%). Unusual G/P combinations (11 strains) were detected in 11.7% of all strains, of which, G1P[4] was the most prevalent, accounting for 5.6% of the total. Several combinations of G and P types were observed in this study, suggesting a complex rotavirus infection pattern in Vietnam. This study has provided for the first time clear indication on the circulating G and P genotypes among hospitalized children in Ho Chi Minh City, Vietnam. The results suggest that these viral infections are prevalent among hospitalized children and that the four most common worldwide G types as well as the four most common G-P combinations were also infecting children in Ho Chi Minh City, Vietnam. This result could have important implications for rotavirus vaccine programs and for understanding the epidemiological characteristics of human rotavirus in Ho Chi Minh City, Vietnam.

Viruses causing gastroenteritis

Acute gastroenteritis is one of the most common diseases in humans worldwide. Viruses are recognized as important causes of this disease, particularly in children. Since the Norwalk virus was identified as a cause of gastroenteritis, the number of viral agents associated with diarrheal disease in humans has steadily increased. Rotavirus is the most common cause of severe diarrhea in children under 5 years of age. Astrovirus, calicivirus and enteric adenovirus are also important etiologic agents of acute gastroenteritis. Other viruses, such as toroviruses, coronaviruses, picobirnaviruses and pestiviruses, are increasingly being identified as causative agents of diarrhea. In recent years, the availability of diagnostic tests, mainly immunoassays or molecular biology techniques, has increased our understanding of this group of viruses. The future development of a safe and highly effective vaccine against rotavirus could prevent, at least, cases of severe diarrhea and reduce mortality from this disease.

Genogroup characterization of reemerging serotype G9 human rotavirus strain 95H115 in comparison with earlier G9 and other human prototype strains

Serotype G9 human rotaviruses have emerged globally since the mid-1990s. The 95H115 strain was derived from a stool specimen collected in Japan in the 1994-95 season, thus it is the earliest of the globally reemerging G9 human rotaviruses that were adapted to cell culture. Genogrouping by RNA-RNA hybridization was performed to examine the genetic background of 95H115. The 95H115 strain belonged to the Wa genogroup, the most common human rotavirus genogroup, and it had a high degree of homology with AU32 and WI61, the prototype G9 isolates in the 1980s. However, the divergent genomic RNA constellation as indicated by the aberrant hybridization patterns between 95H115 and earlier G9 strains served as further evidence that 95H115 was not a direct descendant of the prototype strains in the '80s.

Rotavirus vaccines--an update

Rotavirus vaccines offer the best hope to reduce the toll of acute rotaviral gastroenteritis in both developed and developing countries. An association with intussusception (IS) led to the withdrawal of the first licensed rotavirus vaccine in the USA in 1999, forcing a re-evaluation of the safety profile of potentially lifesaving vaccines. Development of new rotavirus vaccine candidates has continued, with a bovine-human reassortant vaccine and an attenuated human monovalent vaccine commencing Phase III trials. Several other candidates are in early Phase I and II clinical trials. The creation of innovative funding strategies to support vaccine development and production, specifically in developing countries, aim to make vaccines available where rotavirus causes the greatest impact.

VP7 gene polymorphism of serotype G9 rotavirus strains and its impact on G genotype determination by PCR

Rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide. Surveillance of rotavirus serotypes/genotypes (both VP7[G] and VP4[P]) is in progress globally in which polymerase chain reaction (PCR) has been the assay of choice. We investigated polymorphism of the VP7 gene of serotype G9 rotavirus strains and its impact on the determination of VP7 gene genotype by PCR assay. By VP7 gene sequence analysis, we and others have previously shown that the G9 rotavirus strains belong to one of three VP7 gene lineages. By PCR assay using three different sets of commonly used primers specific for G1-4, 8 and 9, 23 Brazilian G9 strains and 5 well-characterized prototype G9 strains which collectively represented all three VP7 gene lineages were typed as: (i). G3; (ii). G4; (iii). G9; (iv). G3 and G9; or (v). G9 and G4 depending on a primer pool employed. This phenomenon appeared to be due to: (i). a VP7 gene lineage-specific polymorphism, more specifically mutation(s) in the primer binding region of the VP7 gene of G9 strain; and (ii). the magnitude of difference in nucleotide homology at respective primer binding site between homotypic (G9) and heterotypic (G3 or G4) primers present in a primer pool employed.

Generation and characterization of six single VP4 gene substitution reassortant rotavirus vaccine candidates: each bears a single human rotavirus VP4 gene encoding P serotype 1A[8] or 1B[4] and the remaining 10 genes of rhesus monkey rotavirus MMU18006 or bovine rotavirus UK

The global disease burden of rotavirus diarrhea in infants and young children has stimulated interest in the biological and clinical characteristics of these agents, leading to intensive efforts to develop a vaccine. A rhesus rotavirus (RRV)-based quadrivalent vaccine ("RotaShield") was licensed and administered to about 1 million infants and found to be highly effective. However, it was withdrawn because of a link with intussusception. This vaccine was developed according to a modified "Jennerian" approach in which one of the two major outer capsid proteins (VP7) shares neutralization specificity with one of the four epidemiologically important human rotavirus serotypes. The other outer capsid protein (VP4) is derived solely from RRV and is distinct from the VP4 of the four human rotavirus serotypes of epidemiologic importance. In an effort to further increase the immunogenicity of the existing VP7-based RRV quadrivalent vaccine, we generated three single VP4 gene substitution reassortant rotavirus candidate vaccines, each of which bears a single human rotavirus VP4 gene encoding P serotype 1A[8] or 1B[4] specificity while the remaining 10 genes are derived from the rhesus rotavirus. By incorporating one or two of these strains into the quadrivalent vaccine, a pentavalent or hexavalent RRV-based vaccine could be formulated thus providing antigenic coverage not only for VP7 serotype 1, 2, 3 and 4 but also for VP4 serotype 1A[8] or 1B[4], thus possibly augmenting its immunogenicity. Similarly, three single VP4 gene (P1A[8] or P1B[4]) substitution reassortants have also been generated in a background of 10 bovine (UK) rotavirus genes for addition to a second generation UK-based quadrivalent vaccine.

Detection of a human rotavirus with G12 and P[9] specificity in Thailand

G12 rotavirus has not been detected anywhere in the world since the first detection of a human strain, L26 (G12, P1B[4]), in the Philippines in 1990. In this study, we isolated a human rotavirus (strain T152) with a VP7 of G12 specificity from the stool of an 11-month-old diarrheic patient in Thailand. The strain T152 exhibited a long RNA pattern and subgroup I specificity. In the comparison of the nucleotide and amino acid sequences of the VP7 gene of strain T152 with those of rotaviruses with different G type specificities, strain T152 showed the highest identity, 90.9 and 93.9%, respectively, to G12 prototype strain L26. In contrast, the VP4 gene of strain T152 showed the highest identity with P[9] specificity of human strains K8 and AU-1 and feline strains Cat2 and FRV-1, with homologies of 89.3 to 90.6% at the nucleotide level and 93.9 to 95.6% at the amino acid level. Thus, strain T152 was found to be a natural reassortant strain with G12 and P[9] specificities.

Characterization of nontypeable rotavirus strains from the United States: identification of a new rotavirus reassortant (P2A[6],G12) and rare P3[9] strains related to bovine rotaviruses

Among 1316 rotavirus specimens collected during strain surveillance in the United States from 1996 to 1999, most strains (95%) belonged to the common types (G1 to G4 and G9), while 5% were mixed infections of common serotypes, rare strains, or not completely typeable. In this report, 2 rare (P[9],G3) and 2 partially typeable (P[6],G?; P[9],G?) strains from that study were further characterized. The P[6] strain was virtually indistinguishable by hybridization analysis in 10 of its 11 gene segments with recently isolated P2A[6],G9 strains (e.g., U.S.1205) from the United States, but had a distinct VP7 gene homologous (94.7% a.a. and 90.2% nt) to the cognate gene from P1B[4],G12 reference strain L26. Thus, this serotype P2A[6],G12 strain represents a previously unrecognized reassortant. Three P3[9] strains were homologous (97.8-98.2% aa) in the VP8 region of VP4 to the P3[9],G3 feline-like reference strain AU-1, but had a high level of genome homology to Italian bovine-like, P3[9],G3 and P3[9],G6 rotavirus strains. Two of the U.S. P3[9] strains were confirmed to be type G3 (97.2-98.2% VP7 aa homology with reference G3 strain AU-1), while the other was most similar to Italian bovine-like strain PA151 (P3[9],G6), sharing 99.0% a.a. homology in VP7. Cross-neutralization studies confirmed all serotype assignments and represented the first detection of these rotavirus serotypes in the United States. The NSP4 genes of all U.S. P3[9] strains and rotavirus PA151 were most closely related to the bovine and equine branch within the DS-1 lineage, consistent with an animal origin. These results demonstrate that rare strains with P and G serotypes distinct from those of experimental rotavirus vaccines circulate in the United States, making it important to understand whether current vaccine candidates protect against these strains.

Emergence of G9 P[6] human rotaviruses in Argentina: phylogenetic relationships among G9 strains

Because rotavirus diarrhea can be reduced through vaccination and because current vaccine candidates provide protection against only the most common G antigenic types (G1 to G4), detection of uncommon G types is one of the main goals of rotavirus surveillance. After a 2-year nationwide rotavirus surveillance study in Argentina concluded, surveillance was continued and an increase of G9 prevalence in several Argentine cities was detected. During this period G9 strains predominated in the south, and a gradient of decreasing G9 prevalence was observed from south to north (41 to 0%). Sequence analysis of gene 9, encoding the G antigen, showed that Argentine strains cluster with most G9 isolates from other countries, showing less than 2% nucleotide divergence among them, but are distinctive from them in that they present some unique amino acid changes. Our results agree with reports of increased G9 prevalence in other parts of the world, suggesting the need to incorporate G9 into candidate rotavirus vaccines.

Molecular epidemiology of rotaviruses in Nigeria: detection of unusual strains with G2P[6] and G8P[1] specificities

During an epidemiological study on rotaviruses among diarrheic children in the northeastern and middle belt regions of Nigeria, the distribution of G and P types was investigated in 127 stool specimens. By PCR G typing, the G type of rotaviruses in 97 samples was identified. Interestingly, an unusual G8 type, as well as common G1, G2, and G3 types, was detected more frequently (31 of 112; 27.7%). Eleven samples contained multiple G types, and a G9 strain (Bulumkutu) was identified for one of the probable mixed infections. In PCR P typing, P[6] was detected most frequently, P[8] being the second most common type, while the P type of 73 samples could not be identified. One rotavirus strain with a G8 type specificity could be cultivated in cell culture, and the P type of this strain was found to be P[1], which is usually carried by bovine strains. When the combinations of G and P types were examined, the unusual strains G2P[6] and G8P[1] were often identified. Sequence analysis was performed for the VP7 gene of the G9 strain Bulumkutu and the VP4 and VP7 genes of G8P[1] strain HMG035. The VP7 sequence of the Nigerian serotype G9 was more closely related to that of a Brazilian strain than to those of other African strains. The VP7 and VP4 genes of G8P[1] strain HMG035 were found to be very similar to that of a Thai bovine strain A5, suggesting that bovine strains may have been transmitted directly to humans. These results highlight an unexpected diversity among rotavirus strains in Nigeria and emphasize the need for further serological and genetic surveys on more rotavirus strains in African countries, including Nigeria.

Rotavirus genotypes P[4]G9, P[6]G9, and P[8]G9 in hospitalized children with acute gastroenteritis in Rio de Janeiro, Brazil

Fifty-three rotavirus-positive fecal specimens from children with diarrhea admitted to a Rio de Janeiro, Brazil, children's hospital between January 1997 and December 1998 were characterized for P and G types by using reverse transcription-PCR. Genotype P[4]G2 accounted for 21% of isolates, while uncommon genotypes P[8]G9, P[6]G9, and P[4]G9 accounted for 13% of the isolates.

Apparent re-emergence of serotype G9 in 1995 among rotaviruses recovered from Japanese children hospitalized with acute gastroenteritis

Serotype G9 rotaviruses have been detected in about 0.5% of the circulating strains worldwide. However, G9 strains emerged globally in the middle of the 90s and thereafter. A rotavirus, contained in stool specimen 95H115, possessing a G9 VP7 emerged in Japan in the 1994-1995 season for the first time after a 9-year interval since prototype G9 strains AU32 and F45 were discovered in the 1985-1986 season. In comparison with other G9 VP7 genes thus far published, the sequencing of the VP7 genes of AU32 and 95H115 revealed that the 95H115 VP7 gene did not directly evolve from the AU32 VP7 gene but was much more closely related to the contemporary G9 VP7 genes found in the United States of America. Thus, recently emerging G9 VP7 genes were not direct descendants of the VP7 genes of the prototype strains in the 80s, rather they evolved independently into 4 phylogenetic clusters from a common ancestor.

Rotavirus strain diversity in Blantyre, Malawi, from 1997 to 1999

In a 2-year study of viral gastroenteritis in children in Blantyre, Malawi, the diversity of rotavirus strains was investigated by using electropherotyping, reverse transcription-PCR amplification of the VP7 and VP4 genes (G and P genotyping), and nucleotide sequencing. Of 414 rotavirus strains characterized, the following strain types were identified: P[8], G1 (n = 111; 26.8%); P[6], G8 (n = 110; 26.6%); P[8], G3 (n = 93; 22.5%); P[4], G8 (n = 31; 7.5%); P[8], G4 (n = 21; 5.1%); P[6], G3 (n = 12; 2.9%); P[6], G1 (n = 7; 1.7%); P[6], G9 (n = 3; 0.7%); P[6], G4 (n = 3; 0.7%); P[4], G3 (n = 1; 0.2%); and mixed (n = 15; 3.6%). While all strains could be assigned a G type, seven strains (1.7%) remained P nontypeable. The majority of serotype G8 strains and all serotype G9 strains had short electropherotype profiles. All remaining typeable strains had long electropherotypes. Divergent serotype G1 rotaviruses, which contained multiple base substitutions in the 9T-1 primer binding site, were commonly identified in the second year of surveillance. Serotype G2 was not identified. Overall, G8 was the most frequently identified VP7 serotype (n = 144; 34.8%) and P[8] was the most frequently detected VP4 genotype (n = 227; 54.8%). Partial sequence analysis of the VP4 gene of genotype P[8] rotaviruses identified three distinct clusters, which predominantly (but not exclusively) comprised strains belonging to a distinct VP7 serotype (G1, G3, or G4). As a result of mutations in the 1T-1 primer binding site, strains belonging to each cluster required a separate primer for efficient typing. One cluster, represented by P[8], G4 strain OP354, was highly divergent from the established Wa and F45 VP4 P[8] lineages. As is the case for some other countries, the diversity of rotaviruses in Malawi implies that rotavirus vaccines in development will need to protect against a wider panel of serotypes than originally envisioned.

Rotavirus strains bearing genotype G9 or P[9] recovered from Brazilian children with diarrhea from 1997 to 1999

Human rotavirus strains belonging to genotype G9 or P[9] were detected in a collection of stool specimens from children with diarrhea in two cities of the state of Rio de Janeiro, Brazil, between March 1997 and December 1999. G9 strains were first detected in April 1997 and remained prevalent until the end of the study, at a frequency of 15.9% (n = 157). A high percentage of VP7 nucleotide (99.0 to 99.5%) and deduced amino acid identity (98.6 to 99.1%) was found between three randomly selected Brazilian G9 strains and the American G9 strain US1205. A novel G9:P[4] genotype combination was detected in addition to G9:P[8] and G9:P[6], demonstrating that this G genotype may undergo constant genetic reassortment in nature. The P[9] rotavirus strains constituted 10.2%, the majority of which were detected between April and July 1997. The RNA electrophoretic migration pattern of the G3:P[9] strains resembled that of AU-1 virus (G3:P3[9]), suggesting a genetic similarity between the Brazilian G3:P[9] strains and the Japanese virus, which is similar to a feline rotavirus genetically.

Epidemiological patterns of rotaviruses causing severe gastroenteritis in young children throughout Australia from 1993 to 1996

Rotavirus strains that caused severe diarrhea in 4,634 (2,533 male) children aged less than 5 years and admitted to major hospitals in eight centers throughout Australia from 1993 to 1996 were subject to antigenic and genetic analyses. The G serotypes of rotaviruses were identified in 81.9% (3,793 of 4,634) children. They included 67.8% (from 3,143 children) serotype G1 isolates (containing 46 electropherotypes), 11.5% (from 531 children) serotype G2 isolates (27 electropherotypes), 0.8% (from 39 children) serotype G3 isolates (8 electropherotypes), and 1.6% (from 76 children) serotype G4 isolates (9 electropherotypes). G6 (two strains) and G8 (two strains) isolates were identified during the same period. G1 serotypes were predominant in all centers, with intermittent epidemics of G2 serotypes and sporadic detection of G3 and G4 strains. With the exception of two strains (typed as G1P2A[6] and G2P2A[6]) all serotype G1, G3, and G4 strains were P1A[8] and all serotype G2 strains were P1B[4]. Two contrasting epidemiological patterns were identified. In all temperate climates rotavirus incidence peaked during the colder months. The genetic complexity of strains (as judged by electropherotype) was greatest in centers with large populations. Identical electropherotypes appeared each winter in more than one center, apparently indicating the spread of some strains both from west to east and from east to west. Centers caring for children in small aboriginal communities showed unpredictable rotavirus peaks unrelated to climate, with widespread dissemination of a few rotavirus strains over distances of more than 1,000 km. Data from continued comprehensive etiological studies of genetic and antigenic variations in rotaviruses that cause severe disease in young children will serve as baseline data for the study of the effect of vaccination on the incidence of severe rotavirus disease and on the emergence of new strains.

Molecular characterization of serotype G9 rotavirus strains from a global collection

Between 1992 and 1998, serotype G9 human rotavirus (RV) strains have been detected in 10 countries, including Thailand, India, Brazil, Bangladesh, Malawi, Italy, France, the United States, the United Kingdom, and Australia, suggesting the possible emergence of the fifth common serotype worldwide. Unlike the previously characterized reference G9 strains (i.e., WI61 and F45), the recent G9 isolates had a variety of gene combinations, raising questions concerning their origin and evolution. To identify the progenitor strain and examine the on-going evolution of the recent G9 strains, we characterized by genetic and antigenic analyses 16 isolates obtained from children with diarrhea in India, Bangladesh, the United States, and Malawi. Specifically, we sequenced their VP7 and NSP4 genes and compared the nucleotide (nt) and deduced amino acid sequences with the reference G9 strains. To identify reassortment, we examined the products of five gene segments; VP4, VP7, and NSP4 genotypes (genes 4, 9, and 10); subgroups (gene 6); electropherotypes (gene 11); and the genogroup profiles of all of the recent G9 isolates. Sequence analysis of the VP7 gene indicated that the recent U.S. P[6],G9 strains were closely related to the Malawian G9 strains (>99% nt identity) but distinct from G9 strains of India ( approximately 97% nt identity), Bangladesh ( approximately 98% nt identity), and the reference strains ( approximately 97% nt identity). Phylogenetic analysis identified a single cluster for the U.S. P[6],G9 strains that may have common progenitors with Malawian P[6],G9 strains whereas separate lineages were defined for the Indian, Bangladeshi, and reference G9 strains. Northern hybridization results indicated that all 11 gene segments of the Malawian P[6],G9 strains hybridized with a probe derived from a U.S. strain of the same genotype and may have the same progenitor, different from the Indian G9 strains, whereas the Bangladesh strains may have evolved from the U.S. G9 progenitors. Overall, our findings suggest that much greater diversity among the newly identified G9 strains has been generated by reassortment between gene segments than through the accumulation of mutations in a single gene.