Rotavirus diarrhea severity is related to the VP4 type in Mexican children

This report is of a community-based case control study to assess whether the severity of acute diarrhea by rotavirus (RV) in young children is associated with a particular VP7 (G) or VP4 (P) RV serotype. Five hundred twenty children younger than 2 years of age with diarrhea lasting less than 3 days were age and gender matched with 520 children with no diarrhea. The G and P serotypes were determined with specific monoclonal antibodies, and the VP4 serotype specificity in a subgroup was confirmed by genotyping. Infection with a G3 serotype led to a higher risk of diarrhea than infection with a G1 serotype. Infection with a G3-nontypeable-P serotype was associated with more severe gastroenteritis than infection with a G3 (or G1) P1A[8] serotype. A child with diarrhea-associated dehydration was almost five times more likely to be infected with a G3-nontypeable-P serotype than a child without dehydration (P < 0.001). Moreover, the two predominant monotypes within serotype P1A[8] had significantly different clinical manifestations. In this study, the severity of RV-associated diarrhea was related to different P serotypes rather than to G serotypes. The relationship between serotype and clinical outcomes seems to be complex and to vary among different geographic areas.     

Prevalence of neutralizing antibodies against different rotavirus serotypes in children with severe rotavirus-induced diarrhea and their mothers

Neutralizing antibody (NAb) responses to different rotavirus serotypes were compared in 64 convalescent-phase serum samples from hospitalized rotavirus-positive children less than 2 years of age and their mothers. Compared to the child patients, the mothers showed significantly higher NAb positivity to animal rotavirus serotypes G3 simian (96.88%), G6 bovine (85.94%), and G10 bovine (25.0%) and to human rotavirus serotypes G8 (79.69%) and G3 (57.81%) (P < 0.01 for each) but not to human serotypes G1, G2, G4, and G9 (P > 0.05). The overall prevalence of NAb among the child patients was low for human rotavirus serotypes G1 (20.31%) and G3 (21.8%). The comparative NAb response in individual mother-child paired serum samples was analyzed against each rotavirus serotype. A substantial number of child patients showed higher NAb titers than their mothers to serotypes G1, G2, G4, and G9, indicating that these serotypes are the major serotypes causing rotavirus diarrhea among the children of Pune, India. In these cases, the mothers were either negative or had lower titers of NAbs than their children. Correlation was observed between the infecting serotype and child patient serum that showed a homologous NAb response at a higher level than that of the mother. It appears that when the level of NAb to a particular serotype is higher among child patients than among their mothers, that serotype is the infecting serotype, and that low titers of NAb among the mothers predispose the children to infection with that serotype, if the serotype is in circulation.     

卢龙县1998年婴幼儿腹泻轮状病毒血清型调查

目的 对河北省卢龙县农村人口中儿童轮状病毒腹泻流行情况进行调查。方法 采用病毒核酸电泳和酶免疫方法对卢龙县1998年轮状病毒腹泻发病季节采集的非菌性腹泻粪便标本进行轮状病毒检测,采用酶免疫和RT-PCR方法对轮状病毒阳性标本进行血清型调查。结果 120份婴幼儿腹泻样本轮状病毒阳性率为39.2%,病毒电泳型全为长型,血清分型发现G3型为流行优势株,占61.7%,其次为G1型占36.2%,G4型占6.4%,轮状病毒腹泻病人最小年龄为2月龄,最大为2岁,男女之比库存1：1.47,结论 卢龙县1998年轮状病毒腹泻流行规律与全国情况基本一致,但流行毒株以G3型为主,与全国以G1型为主不同。     

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.     

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.     

Assessment of the epidemic potential of a new strain of rotavirus associated with the novel G9 serotype which caused an outbreak in the United States for the first time in the 1995-1996 season

Rotavirus causes severe morbidity in developed countries and frequent deaths (> or = 500,000 per year) in less-developed countries. Historically, four serotypes--G1, G2, G3, and G4-have predominated; they are distinguished by one of two surface neutralization antigens (VP7). However, in 1983 and 1984 we described a new rotavirus serotype, designated G9, in five children hospitalized for diarrhea in Philadelphia, Pa. G9 rotavirus was not identified again in the Western Hemisphere until it caused ca. 50% of the rotavirus disease detected in Philadelphia in the 1995-1996 season. This outbreak allowed us to question whether a rotavirus strain completely new to a well-studied community would target either very young infants or older children, cause especially severe disease, or completely displace previously extant serotypes. We observed a significant excess of G9 infections in younger infants (especially in those < 6 months old) that might be attributed to the lack of G9-specific antibodies in mothers. Of further note, six of the seven oldest patients with rotavirus diarrhea were infected with the G9 strains (not significant). However, the age distribution of children with rotavirus did not differ over a 5-year study period regardless of the infecting serotype. Patients with diarrhea associated with G9 strains did not have disease more severe than that caused by the G1, G2, or G3 serotype. G9 strains did not displace the other serotypes but were virtually completely replaced by G1 or G2 serotypes in the three subsequent rotavirus seasons. We conclude that the abrupt appearance of this novel rotavirus serotype did not present a special threat to public health in the community.     

Changing distribution of human rotavirus serotypes during two epidemic outbreaks of gastroenteritis in Campinas, S?o Paulo, Brazil, 2003-2004: Detection of G6 strains

BACKGROUND: Rotavirus serotypes G1-G4 and G9 are the most important agents of severe diarrhea in children worldwide. OBJECTIVE: To characterize rotavirus serotypes/genotypes causing two large outbreaks of diarrhea in Campinas, S?o Paulo, during 2003-2004. STUDY: Rotavirus infection was investigated in 328 stool specimens collected from children and adults with diarrhea by PAGE and RT-PCR and further characterized by semi-nested PCR-typing assays. RESULTS: G3P[8] (26.1%), G9P[8] (18.7%) and G1P[8] (17.9%) were the most frequently detected serotypes/genotypes. G1P[8] was predominant in 2003, but significantly decreased the following year when G3P[8] and G9P[8] prevailed. G5P[8] was identified in about 9% of the typed specimens from each year consistent with its endemic nature in Brazil for over two decades. The other globally common serotypes (G4P[8] and G2P[4]), uncommon G-P combinations, and multiple G serotypes were also found. Rarely found in humans, and not previously reported in Brazil, serotype G6 was identified in three specimens obtained from children in 2004. CONCLUSION: Multiple rotavirus serotypes were observed co-circulating in the city with serotype predominance changing between the two-year study. This study provides pre-vaccine baseline information on locally endemic strains that might help analysis of post-vaccine data.     

Prevalence of Neutralizing Antibodies against Different Rotavirus Serotypes in Children with Severe Rotavirus-Induced Diarrhea and Their Mothers

Neutralizing antibody (NAb) responses to different rotavirus serotypes were compared in 64 convalescent-phase serum samples from hospitalized rotavirus-positive children less than 2 years of age and their mothers. Compared to the child patients, the mothers showed significantly higher NAb positivity to animal rotavirus serotypes G3 simian (96.88%), G6 bovine (85.94%), and G10 bovine (25.0%) and to human rotavirus serotypes G8 (79.69%) and G3 (57.81%) (P < 0.01 for each) but not to human serotypes G1, G2, G4, and G9 (P > 0.05). The overall prevalence of NAb among the child patients was low for human rotavirus serotypes G1 (20.31%) and G3 (21.8%). The comparative NAb response in individual mother-child paired serum samples was analyzed against each rotavirus serotype. A substantial number of child patients showed higher NAb titers than their mothers to serotypes G1, G2, G4, and G9, indicating that these serotypes are the major serotypes causing rotavirus diarrhea among the children of Pune, India. In these cases, the mothers were either negative or had lower titers of NAbs than their children. Correlation was observed between the infecting serotype and child patient serum that showed a homologous NAb response at a higher level than that of the mother. It appears that when the level of NAb to a particular serotype is higher among child patients than among their mothers, that serotype is the infecting serotype, and that low titers of NAb among the mothers predispose the children to infection with that serotype, if the serotype is in circulation.     

Adenovirus types 40 and 41 and rotaviruses associated with diarrhea in children from Guatemala.

From March 1987 to February 1988, fecal excretion of adenovirus types 40 and 41 and rotavirus serotypes in 194 children (age, 0 to 3 years) from a rural community of Guatemala was monitored. In total, 458 samples taken during 385 episodes of diarrhea and 191 specimens obtained during symptom-free periods were examined by enzyme-linked immunosorbent assay. Fifty-seven children hospitalized because of diarrhea were also studied. Among the rural children, 43 (22.2%) excreted adenovirus types 40 and 41 and 20 (10.3%) shed rotaviruses. Adenovirus types 40 and 41 were associated with 54 (14.0%) illnesses, and rotaviruses were associated with 18 (4.7%) illnesses. Asymptomatic infections with adenovirus types 40 and 41 were documented in nine children and with rotaviruses in two children. Fifteen typeable rotaviruses were identified as serotype 2. In the hospital population, 36 (63.2%) children had viral infections. Rotaviruses were identified in 29 (50.9%) and adenovirus types 40 and 41 were identified in 15 (31.2%) of 48 subjects tested. Dual infections by these viruses were found in eight children. Of 22 typeable strains of rotaviruses, 9 (34.6%) were serotype 1, 12 (46.1%) were serotype 2, and 1 (3.8%) was serotype 3. All the children infected with serotype 2 rotavirus were coinfected with other enteric pathogens, while only three (37.5%) of those infected with rotavirus serotype 1 excreted another pathogen. Adenovirus types 40 and 41 are an important cause of gastroenteritis in both ambulatory and hospitalized Guatemalan children. There seems to be a difference in the pathogenicity among rotavirus serotypes.     

Analysis of homotypic and heterotypic serum immune responses to rotavirus proteins following primary rotavirus infection by using the radioimmunoprecipitation technique.

Three sequential serum samples collected from each of 20 young children with a naturally acquired primary rotavirus infection were assayed by the radioimmunoprecipitation technique for immunoglobulin G antibodies to rotavirus structural and nonstructural proteins of the four major human rotavirus serotypes G1, P1A; G2, P1B; G3, P2; and G4, P2. Fourteen children were infected with a serotype G1 rotavirus strain and six children were infected with a serotype G4 rotavirus strain. Sera were collected from each child in the acute and convalescent periods postinfection and also approximately 4 months later. Serum immune responses to rotavirus core antigens VP2 and VP3, to the major inner capsid antigen VP6, to nonstructural proteins NS35, NS28, and NS26, and to the outer capsid neutralization antigen VP4 of all test strains were detected in the majority of patients. These responses do not appear to be influenced by the G type or P type of the rotavirus strain used in the reactions. Homologous responses to the main neutralization antigen VP7 were detected in 93% of patients with serotype G1 infections and 50% of patients with serotype G4 infections. Heterologous VP7 responses were less frequently detected and were restricted to G1, G3, and G4 serotype rotavirus strains. No responses to VP7 of the serotype G2 rotavirus strain were detected in any patients. Heterotypic immune responses to the neutralization antigens, at least following serotype G1 and G4 infections, therefore appear to consist primarily of responses to VP4 rather than to VP7.     

Epidemiological study of the G serotype distribution of group A rotaviruses in Kenya from 1991 to 1994.

An epidemiological study on the G serotype distribution of group A rotaviruses (GARV) isolated in Kenya was carried out in one urban hospital in Nairobi and in two rural hospitals in Nanyuki and Kitui to clarify the prevalent G serotypes before future introduction of the ready licensed rotavirus vaccine in Kenya. A total of 1,431 stool specimens were collected from children, who were mainly outpatients, aged from 0 to 6 years old with acute gastroenteritis from August 1991 to July 1994. Samples positive for GARV by conventional ELISA were then analyzed by subgrouping and serotyping ELISA and by PAGE. To ascertain the G serotypes of viruses in samples that were unable to be typed by serotyping ELISA, polymerase chain reaction was also attempted. The prevalence of GARV was 28.4% in the urban hospital, 22.5% in Nanyuki, and 13.7% in Kitui. Among rotavirus-positive samples, subgroup II rotaviruses were detected in 63.1%, and subgroup I rotaviruses were 25.9%. Serotype G4 was most prevalent, accounting for 41.6% followed by 23.3% of serotype G1, 17.0% of serotype G2, and serotype G3 was rarely isolated. Seven strains of serotype G8/P1B rotavirus was detected for the first time in Kenya by RT-PCR. Eleven specimens with an unusual composition of subgroup, serotype, and electropherotype were atypical GARV in which the P-serotype was P1A, P1B, or P2. Although uncommon GARV serotype G8/P1B and atypical GARV were detected, the four major GARV serotypes, G1 through G4, should be targeted at this moment for vaccination to control this diarrheal disease in Kenya. Continuous monitoring of the G- and P-serotype distribution of GARV should provide important information about the impact of rotavirus vaccination in Kenya.     

Prospective study of diarrheal diseases in Venezuelan children to evaluate the efficacy of rhesus rotavirus vaccine

The efficacy of a rhesus rotavirus vaccine (MMU 18006, serotype 3) against infantile diarrhea was evaluated by active home surveillance of a group of 320 children 1-10 months of age in Caracas, Venezuela. During a 1 year period following oral administration of vaccine or placebo under a double-masked code, over 600 diarrheal episodes were detected. Etiologic studies revealed that heat-stable toxin (ST) producing enterotoxigenic E. coli (ETEC) was the most common diarrheal agent detected (34%) followed by enteropathogenic E. coli (EPEC, 10.9%), heat-labile toxin (LT) producing ETEC (7.6%), rotavirus (6.9%), Cryptosporidium (4.8%) and Campylobacter (1.3%). ST-producing ETEC were also recovered from over 20% of control stool specimens obtained during diarrhea-free periods, whereas EPEC, rotavirus, Cryptosporidium, and Campylobacter were rarely detected in such control specimens. Rotavirus was responsible for about one-half of the more severe cases of diarrhea. Twenty-two of 151 infants who received placebo (14.6%) and eight of 151 receiving a 10(4) PFU dose of vaccine (5.3%) had rotavirus diarrhea during the follow-up period for an efficacy level of 64% against any rotavirus diarrhea. However, vaccine efficacy reached 90% against the more severe cases of rotavirus diarrhea and was noticeably high in the 1-4 month age group. Serotypic analysis of the rotaviruses detected suggests that the resistance induced by the vaccine was type specific since significant protection was only evident against serotype 3 rotaviruses. A 10(3) PFU dose tested initially in 18 children did not appear to protect against rotavirus diarrhea.     

Distribution of human group a rotavirus VP7 and VP4 types circulating in Seoul,Korea between 1998 and 2000

Three hundred forty-eight fecal specimens collected from young children with acute diarrhea in Seoul, Korea between January 1998 and February 2000 were examined for G and P types. Of these, 205 samples (59%) were confirmed as group A rotavirus by ELISA for the detection of VP6 antigen. Confirmed rotavirus isolates were characterized using G serotyping ELISA and RT-PCR methodologies for G and P genotyping of the outer capsid proteins VP7 and VP4, respectively. Serotyping of the outer capsid protein, VP7, revealed G4 as the dominant circulating serotype (41%) followed by G1 (28%) and quite a high incidence of mixed infection (14%). Genotyping of the VP4 protein was carried out on 55 of the rotavirus isolates with the dominant type being P[8] (46%). Of interest were a number of unusual G and P type combinations detected in Korea for the first time, especially the P[4] genotype associated with non-G2 serotypes. There were also a number of P[6] isolates identified including one G2P[6] isolate.     

Group A rotavirus-associated diarrhea in children seeking treatment in Indonesia

BACKGROUND: Globally, group A rotavirus causes significant morbidity and mortality among children. Limited data exist on the epidemiology of rotavirus disease among Indonesian children. OBJECTIVES: We describe the epidemiology of rotavirus-associated diarrhea among Indonesian children <6 years of age, including clinical symptoms and genotypes. STUDY DESIGN: We conducted a hospital-based, case series study at four referral hospitals between February 2004 and February 2005 among children with diarrhea. Rotavirus positivity was defined by a positive result from either EIA or RT-PCR. A semi-nested RT-PCR was used to determine specific rotavirus genotypes. RESULTS: 1660 stools were tested for pathogens. The overall rotavirus prevalence was 45.5%. Children with rotavirus-associated diarrhea were significantly younger (p<0.0001) and more likely to be hospitalized (81.3% versus 72.2%; p<0.0001). Symptoms associated with rotavirus included, vomiting, fever, nausea, fatigue and dehydration, while bloody stool was significantly less common with rotavirus-associated diarrhea. CONCLUSION: Rotavirus was an important contributor of morbidity to our study sample. Rotavirus genotyping demonstrated a temporal shift from G1-G4 to G9, but this was highly associated with the P[8] gene, suggesting that a multivalent rotavirus vaccine, incorporating G9 P[8] antigen, may reduce the burden of diarrheal illnesses among Indonesian children.     

Molecular epidemiology of rotavirus diarrhea among children and adults in Nepal: detection of G12 strains with P[6] or P[8] and a G11P[25] strain

In anticipation of a rotavirus vaccine in Nepal, this study was undertaken to determine the distribution of the G and P serotypes and electropherotypes of rotaviruses in order to examine if there is any emerging serotype or unusual strain circulating in children and adults in Nepal. Of 1,315 diarrheal stool specimens, rotavirus was detected by an enzyme-linked immunosorbent assay in 116 (17%) of 666 patients less than 5 years of age, in 18 (7%) of 260 patients 5 to 14 years of age, and in 19 (5%) of 358 patients 15 years of age and older. Approximately 75% of rotavirus diarrhea occurred in children less than 5 years of age. Approximately 70% of rotaviruses found in each of the three age groups belonged to serotype G1P[8]. Interestingly, there were 29 (20%) G12 rotaviruses carrying either P[8] or P[6] and one (0.7%) G11 rotavirus carrying an unusual P[25] genotype. RNA polyacrylamide gel electrophoresis discriminated 19 strains (electropherotypes), among which there were three codominant strains carrying G1P[8] and long RNA patterns. Five electropherotypes were discriminated among G12 rotaviruses, all of which had long RNA patterns. The fact that 20% of rotaviruses were G12 strains carrying either P[8] or P[6] and had multiple electropherotypes suggest that G12 strains are not more rare strains but that they pose an emerging challenge to current and future vaccines. The presence of multiple strains as defined by electropherotypes suggests the richness of the rotavirus gene pool in Nepal, where unusual strains may continue to emerge.     

河北省卢龙地区2008-2009年度轮状病毒流行病学研究

目的 了解河北省轮状病毒腹泻的流行情况.方法 2008年9月至2009年8月收集卢龙县儿童医院及妇幼保健院5岁以下腹泻住院患儿标本共426份,采用酶联免疫吸附试验（ELISA）检测轮状病毒抗原,阳性标本用反转录-聚合酶链反应（RT-PCR）进行基因分型.结果 426份标本中轮状病毒检出率为47.42%（202/426）.对202份轮状病毒阳性标本进行G/P分型,G3型是主要优势株,占57.9%（117/202）,其次为混合G型感染（16.3%）,G9型（14.9%）,G1型（7.9%）,G4型（1%）,G2型（0.5%）,P基因型最常见的为P[8]占58.4%,其次为P型混合感染占28.7%,P[4]（6.9%）,P[9]（1%）,最常见的G/P组合为G3P[8].结论 轮状病毒是卢龙地区儿童腹泻住院的主要病原,G3P[8]为主要流行株,混合型在该地区多发,且G9血清型在该地区已经成为仅次于G3的第二大优势株.     

Group A rotavirus G type prevalence in two regions of Hungary

Summary Rotaviruses are a major cause of gastroenteritis in children worldwide. Rotaviruses are antigenically complex, with multiple serotypes (G types). The first longitudinal study of group A rotavirus serotype (G type) distribution in Hungary is reported. Neutralizing monoclonal antibodies specific for G1, G2, G3, and G4 were used in an enzyme immunoassay to determine the antigenic variation of group A rotaviruses in two collections of stool specimens assembled from 1984–1992 in Baranya County, southwest Hungary, and from 1988–1992 at the Central Hospital for Infectious Diseases in Budapest. Ninety-two percent of the 1215 virus-positive samples were typed as follows: G1 (81%), G2 (4%), G3 (1%), G4 (5%), or mixed type (1%). G1 was the predominant type during the entire study period with the exception of the 1988/1989 rotavirus season in Baranya County when G4 predominated. Among G1 strains, different electropherotypes were detected with a shift of the predominant G1 electropherotype(s) each 2 to 3 years. G typing from two longitudinal collections established regional differences within Hungary in the prevalence of rotavirus antigenic types among children with rotavirus-associated diarrhea. These are the first longitudinal rotavirus typing results for Hungary and Central Europe.     

Culture adaptation and characterization of group A rotaviruses causing diarrheal illnesses in Bangladesh from 1985 to 1986.

Group A rotaviruses collected between 1985 and 1986 during comprehensive surveillance of treated diarrheal episodes occurring in a rural Bangladesh population were culture adapted and characterized by electropherotype, serotype, and subgroup. Of 454 episodes of rotavirus-associated diarrhea, rotaviruses were culture adapted from 381 (84%), and 335 contained 11 electrophoretically identical segments in unpassaged and cultured preparations. These 335 comprised 69 different electropherotypes with between 1 (32 isolates) and 79 representatives. The persistence of specific rotavirus strains within the study population, as defined by the detection of viruses with particular electropherotypes, was generally limited to a period of only a few months. All 335 isolates were serotyped by neutralization with hyperimmune antisera to prototype rotavirus strains representative of serotypes 1 to 4, i.e., Wa, DS-1, P, and ST-3. It was found that 80, 48, 119, and 88 isolates belonged to serotypes 1 to 4, respectively. The concentrations of hyperimmune antisera required to neutralize these isolates, however, were at least threefold greater than those needed to neutralize the homologous strains. Therefore, the isolates appeared to have altered neutralization epitopes from their prototype strains. Furthermore, the serotype 4 isolates were consistently shown to be much more closely related to the serotype 4B VA70 strain than the serotype 4A ST-3 strain. All but two isolates identified as serotypes 1, 3, or 4 had long electropherotypes and were subgroup II, and all but one serotype 2 isolate were subgroup I and had short electropherotypes. The three disparate strains appeared to be genetic reassortants. Evidence is presented that dual infections required for reassortant formation were not uncommon. Thus, formation of multiple reassortants may have been a cause for the observed rapid shift in viral strains within the study population.     

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.