Clinical and molecular epidemiology of norovirus infection in childhood diarrhea in China

A prospective investigation was carried out among pediatric outpatients and inpatients with acute non‐dysenteric diarrhea between August, 2008 and July, 2009 in Shanghai, Hangzhou, Chongqing, and Tianjin, China. One step real‐time RT‐PCR was used for detection of norovirus (NoV) genogroups I and II (GI, GII). The NoV genotypes were classified based on partial capsid sequences. Rotavirus (RV) was detected in parallel. Among 4,123 fecal samples from outpatients, 1,067 (25.9%) were NoV‐positive, of which 1,051 (98.5%) belonged to GII and 1,309 (31.7%) were RV‐positive. In the inpatient group (n = 317), 25.6% were NoV‐positive and 41.6% were RV‐positive. Four hundred and fifty‐one out of 1,067 NoV‐positive strains were sequenced and genotyped and 6 typed strains were GI (3 GI.3, 2 GI.5, 1 GI.4) and 445 typed strains were GII. GII strains clustered into nine genotypes including GII.4 2006b (69.2%), the only GII.4 variant identified in this study, followed by GII.3 (23.8%), GII.6 (3.6%), GII.12 (1.3%), GII.2 (0.9%), GII.13 (0.4%), GII.14 (0.2%), GII.7 (0.2%), and GII.16 (0.2%). A peak of NoV infections was observed during the cold season in Tianjin, while NoV activity was higher between late summer and autumn and lower during winter in Shanghai, Hangzhou, and Chongqing. NoV is a common causative agent of childhood diarrhea in China and the seasons of NoV‐associated diarrhea varies between regions. The results show that NoV GII.4 2006b was the predominant strain circulating in China between 2008 and 2009. J. Med. Virol. 84:145–151, 2011. © 2011 Wiley Periodicals, Inc.     

南京地区婴幼儿杯状病毒感染的分子流行病学研究

目的了解南京地区婴幼儿杯状病毒腹泻的感染状况、临床表现以及分子流行病学特征。方法采集2010年7月至2011年6月南京医科大学附属南京儿童医院5岁以下腹泻患儿粪便标本及儿童保健中心健康婴幼儿粪便标本各428份。采用反转录-聚合酶链反应（RT—PCR）检测杯状病毒,测序确定其基因型别。结果428份腹泻样本中有63份为杯状病毒阳性,检出率为14．72％。其中诺如病毒GⅡ型58例,未检出诺如病毒GI型,札如病毒5例,以诺如病毒GⅡ-42006b型为主要流行株。428份健康对照组标本杯状病毒检出19例,诺如病毒6例,札如病毒11例,2例为诺如病毒GⅡ型和札如病毒混合感染。结论南京地区婴幼儿中存在不同基因型杯状病毒感染,流行毒株以GⅡ-2006b为主。     

Epidemiological study of human calicivirus infection in children with gastroenteritis in Lanzhou from 2001 to 2007

Stool specimens were collected from 1,195 young children with acute diarrhea in Lanzhou, China, from 2001 to 2007. RT-PCR was used to detect human calicivirus (HucV). One hundred seventeen specimens were found positive for HucV. The infection rate was noticeably higher during 2006–2007 compared to the other years studied. Ninety-six specimens were sequenced to determine the genotypes of HucV. Eighty-six were norovirus and 10 were sapovirus, while GII/4 was the predominant strain of NV, followed by GII/3. The subtype of NV GII/4 changed from the Farmington Hills strain to the Bristol strain, and then to the Hunter strain and variant 2006b strain, over time. Variant 2006b has become the major epidemic strain in Lanzhou and should be closely monitored in the coming years.     

Detection of diarrheal viruses circulating in adult patients in Thailand

A total of 332 fecal specimens collected during January-December 2008 from adult patients with diarrhea were screened for group A and C rotaviruses, noroviruses GI and GII, sapovirus, Aichi virus, human parechovirus, enterovirus, adenovirus and astrovirus by RT-multiplex PCR. The detection rate for diarrheal viruses was 4.2 %. Adenovirus and enterovirus were equally detected as the most predominant viruses, with prevalence of 1.2 %, followed by Aichi virus (0.9 %) and norovirus GII (0.6 %). Mixed infection with norovirus GII and human parechovirus was also detected (0.3 %). This study provides epidemiological data for a wide variety of diarrheal viruses circulating in adult patients with diarrhea in Chiang Mai, Thailand.     

Surveillance of pathogens causing gastroenteritis and characterization of norovirus and sapovirus strains in Shenzhen,China, during 2011

Viral gastroenteritis is one of the most common diseases in humans, and it is primarily caused by rotaviruses (RVs), astroviruses (AstVs), adenoviruses (AdVs), noroviruses (NoVs), and sapoviruses (SaVs). In this study, we determined the distribution of viral gastroenteritis and human calicivirus (HuCVs) in acute gastroenteritis patients in Shenzhen, China, during 2011. Real-time RT-PCR was used to detect norovirus (NoV), group A rotavirus (RV), adenovirus (AdV), and astrovirus (AstV). From a total of 983 fecal samples, NoV was detected in 210 (21.4 %); RoV in 173 (17.6 %); AstV in 10 (1.0 %); and AdV in 15 (1.5 %). Mixed infections involving two NoVs were found in 21 of the 387 pathogen-positive stool specimens. NoV and SaV genotypes were further tested using RT-PCRs and molecular typing and phylogenetic analysis were then performed based on the ORF1-ORF2 region for NoV and a conserved nucleotide sequence in the capsid gene for SaV. Of the 68 typed strains that were sequenced and genotyped, five were NoV G1 (7.5 %) and 63 were NoV GII (96.6 %). GII strains were clustered into five genotypes, including GII.4 (65.1 %; 36 GII.4 2006b and five GII.4 New Orleans), GII.3 (28.6 %), GII.2 (3.2 %), GII.6 (1.6 %), and GII.1 (1.6 %). While all fecal specimens were tested for SaVs, 15 (1.5 %) were positive, and of these, 12 isolates belonged to G1.2, and the remaining three SaV strains belonged to the SaV GII genogroup. Although various HuCVs were detected in acute gastroenteritis patients, NoV GII.4 2006b was more prevalent than the other HuCVs.     

Genotype distribution of norovirus around the emergence of Sydney_2012 and the antigenic drift of contemporary GII.4 epidemic strains

BackgroundThe pattern of epochal evolution of NoV is ongoing, while novel GII.4 variants emerge and cause new pandemics. Since, the emergence in March 2012, Sydney_2012 had replaced GII.4-2009 as the primary NoV strain in most countries in the northern hemisphere by November 2012.ObjectivesTo determine the genotype distribution around the emergence of Sydney_2012 and to investigate the underlying evolution mechanisms of the contemporary GII.4 strains.Study designFrom January 2012 to December 2013, molecular epidemiology of norovirus in 846 adults (≥16 years) in Shanghai were conducted. The VP1 proteins of the contemporary GII.4 strains (Den_Haag_2006b, New_Orleans_2009 and Sydney_2012) were expressed in vitro and purified. Receptor binding patterns of these three epidemic strains were determined through histo-blood group antigen (HBGA) binding assays. Convalescent serum from patients infected with GII.4 epidemic strains were employed to investigate the role of antigenic drift in the persistence of GII.4 epidemic strains through receptor-binding blockade assays.ResultsEpidemiological studies revealed that Sydeny_2012 has completely replaced Den_Haag_2006b and New_Orleans_2009 and has been the dominant circulating strain in Shanghai since its emergence in October 2012. Interestingly, Den_Haag_2006b and New_Orleans_2009 have been co-circulating in Shanghai before the emergence of Sydeny_2012. The contemporary GII.4 epidemic norovirus strains displayed commonly high tropism to the histo-blood group antigen receptors, whereas Sydeny_2012 was antigenically different from Den_Haag_2006b and New_Orleans_2009.ConclusionsAntigenic drift, rather than receptor switch, played a key role in the emergence and spreading of Sydney_2012. The contemporary GII.4 strains were evolving via epochal evolution without altered ligand binding profiles.     

Prevalence and genetic diversity of norovirus infection in Tunisian children (2007–2010)

Viral gastroenteritis can be a life‐threatening disease in infants and young children, especially in developing countries. The aim of this study was to continue the epidemiological surveillance of norovirus (NoV) infections in Tunisian children suffering from acute gastroenteritis. Surveillance was initiated in January 2003, to monitor potential variations in strains over time, in terms of frequency and diversity of NoV genotypes, and more particularly the potential emergence of new GII.4 variants following the 2004 Hunter variant. From April 2007 to April 2010, a total of 407 stool specimens were collected from sporadic cases (238 inpatients and 169 outpatients). Furthermore, 28 stool samples were collected from children involved in 3 gastroenteritis outbreaks. Stool specimens were screened for NoV genogroup I (GI) and II (GII) by RT‐PCR. NoV strains were genotyped, and variants identified, based on sequence and phylogenetic analyses of the polymerase and capsid genes. NoVs were detected in 38 sporadic cases (9.3%) and 21 epidemic cases (75%). Great diversity was observed throughout the period, with seven distinct NoV genotypes characterized in sporadic cases, and three in outbreaks. GIIb/II.3 and GII.4 were predominant globally, with fluctuations of their prevalence over time. Interestingly, the Hunter variant, which was the unique GII.4 variant observed from 2003 to April 2007 in the region of Monastir, was replaced by the 2006b variant. NoV is an important enteropathogen responsible for viral gastroenteritis among infants and children in Tunisia, and the infecting strains between 2007 and 2010 were different from those in previous years. J. Med. Virol. 85: 1100–1110, 2013. © 2013 Wiley Periodicals, Inc.     

Molecular epidemiology of norovirus gastroenteritis outbreaks in New Zealand from 2002-2009

Noroviruses are the most common cause of acute non-bacterial gastroenteritis outbreaks worldwide, including New Zealand. New Zealand has a population of 4.4 million, which allows for centralized outbreak surveillance and a Norovirus Reference Laboratory, which facilitates efficient diagnosis, surveillance, and tracking of norovirus outbreaks. Norovirus outbreak strains are identified, sequenced, and compared with international reference strains. Between January 2002 and December 2009, 1,206 laboratory-confirmed norovirus outbreaks were recorded. The predominant outbreak settings were healthcare institutions for the elderly and acute care patients. Other outbreak settings included catering establishments, cruise ships, homes, community events, school camps, child-related settings, and consumption of contaminated shellfish. Of the 1,206 outbreaks, 105 (8.7%) were caused by norovirus genogroup I (GI) strains, 1,085 (89.9%) were caused by genogroup II (GII) strains, and both GI and GII strains were detected in 9 (0.8%) outbreaks. The genogroup was not identified in 7 (0.6%) outbreaks. A range of norovirus genotypes, including GI genotypes 1-6, GII genotypes 2-8, and GII.12, were associated with these outbreaks. The predominant genotype was GII.4, which was identified in 825 (68.4%) outbreaks. Norovirus GII.4 variant strains, including 2002 (Farmington Hills), 2004 (Hunter), 2006a (Laurens, Yerseke), 2006b (Minerva), and 2010 (New Orleans) implicated in overseas outbreaks also occurred in New Zealand, providing evidence of global spread.     

Association between Norovirus and Rotavirus Infection and Histo-Blood Group Antigen Types in Vietnamese Children

Norovirus and rotavirus are the two most important causes of acute gastroenteritis in children worldwide. Both norovirus and rotavirus recognize human histo-blood group antigens (HBGAs), and multiple binding patterns for HBGAs have been reported. To explore the role of HBGAs in host susceptibility to norovirus and rotavirus, we conducted a cross-sectional study in children hospitalized with diarrhea in northern Vietnam from September 2010 through September 2012. Of 260 children with paired stool and saliva samples, 158 (61%) were classified as HBGA secretors (Le^a−b+), 31 (12%) were nonsecretors (Le^a+b−), and 71 (27%) were partial secretors (Le^a+b+). Norovirus was detected in 50 patients (19%), with viral genotypes GII.3 (n = 28) and GII.4 (n = 22) being the most common. All children infected with norovirus strains of genotype GII.4 were either HBGA secretors or partial secretors. Of the 28 GII.3 cases, 12 involved HBGA secretors, 11 partial secretors, and 5 nonsecretors. A total of 85 children tested positive for rotavirus, 74 of whom were infected with genotype P[8], 5 with P[4], and 6 with P[6]; all were HBGA secretors or partial secretors. This is the first epidemiological study demonstrating in a population that HBGA phenotype is a key susceptibility factor for both norovirus and rotavirus infections in children.     

Surveillance of norovirus in Portugal and the emergence of the Sydney variant, 2011–2013

This report presents the results of the national surveillance system of diarrhea etiology of the National Institute of Health of Portugal concerning norovirus (NoV) during a two-year period, May 2011–2013. Of the total 580 stool samples collected from patients hospitalized for acute diarrhea in 13 Hospitals of Portugal, 67 (11.6%) tested positive for NoV. From May 2011 to March 2012 the GII.4 variant New Orleans 2009 was the most predominant strain having been replaced by the new GII.4 variant Sydney 2012 since then till the end of the survey. To our knowledge this is the first study showing the circulation of GII.4 as the norovirus strain most commonly associated to gastroenteritis and the first to report the replacement of GII.4 New Orleans by GII.4 Sydney 2012 variant in Portugal.     

Molecular epidemiology of noroviruses in children and adults with acute gastroenteritis in Wuhan, China, 2007-2010

To study epidemiological features and genetic characteristics of noroviruses in children and adults with acute gastroenteritis, fecal specimens were collected in three hospitals from Jan. 2007 to May 2010 in Wuhan, China. Noroviruses were detected in 25.9 % (286/1103) and 24.6 % (202/822) of the specimens from children and adults, respectively, with genogroup II (GII) being predominant (99.2 %). The most frequent genotype among GII strains was GII.4 (2006b variant) (77.3 %) (72.0 % in children and 87.9 % in adults), followed by GII.3 (15.0 %) and GII.6 (3.4 %). Potential recombinant genotypes (polymerase/capsid) were detected in 51 GII strains (15.9 %), including the most frequent type, GII.12/GII.3 (28 strains), and GII.16/GII.2, detected for the first time in China, which were found in only children. The results indicated that genetically similar noroviruses were circulating among children and adults as a cause of gastroenteritis, except for some recombinant genotypes.     

Molecular epidemiology of noroviruses associated with acute sporadic gastroenteritis in children: Global distribution of genogroups,genotypes and GII.4 variants

Noroviruses are a leading cause of epidemic and sporadic acute gastroenteritis worldwide. The development of sensitive molecular diagnostic techniques has revolutionized our understanding of norovirus epidemiology over the past two decades, but norovirus strain types associated with sporadic gastroenteritis remain poorly described. Therefore, we conducted a systematic review of studies performed after 2000 to clarify the genotypic distribution of noroviruses in children (≤18 years of age) with sporadic acute gastroenteritis. Genogroup GII norovirus was the most prevalent, accounting for 96% of all sporadic infections. GII.4 was the most prevalent genotype, accounting for 70% of the capsid genotypes and 60% of the polymerase genotypes, followed by the capsid genotype GII.3 (16%) and the polymerase genotype GII.b (14%). The most common ORF1/ORF2 inter-genotype recombinants were GII.b, GII.12, and GII.4 polymerase genotypes combined with the capsid genotype GII.3, accounting for 19% of all genotyped strains. The distribution of GII.4 variants over the last decade was dominated by successive circulation of GII.4/2002, GII.4/2004, GII.4/2006b, and GII.4/2008 with GII.4/2006b continuing to date. Genotypes GII.4 and GII.3 have predominated in children during the past decade; this is most notable in the global emergence of GII.4 variant noroviruses. As the burden of rotavirus disease decreases following the introduction of childhood immunization programs, the relative importance of norovirus in the etiology of acute childhood gastroenteritis will likely increase. In order for a successful norovirus vaccine to be developed, it should provide immunity against strains with capsid genotypes GII.4 and GII.3.     

Molecular epidemiology of norovirus infection among children with acute gastroenteritis in Shanghai,China, 2001–2005

Norovirus is one of the major causes of outbreaks and sporadic cases of acute gastroenteritis in young children worldwide. Obtaining local baseline information regarding this virus is important for developing and evaluating prevention strategies of norovirus transmission in children. The age, seasonal distribution and circulating genotypes of norovirus in Shanghai, China, between 2001 and 2005 were determined. Of 5411 stool specimens collected from children under 5 years of age who were hospitalized with acute gastroenteritis 3,975 were rotavirus‐negative, indicating the presence of another causative agent. From these specimens, 484 were selected at random for genotyping, and 45 were norovirus‐positive. Norovirus infection was detected in all age groups, but infants less than 6 months old showed the lowest prevalence (5.4%). Norovirus infections peaked from August to November. Among the 37 identified norovirus strains, 2 were GII‐3, 2 were GII‐7, and 33 were GII‐4 genotypes. This study demonstrated the impact of norovirus infection causing acute gastroenteritis in hospitalized children and the importance of vaccination against norovirus diarrhea in Shanghai, China. J. Med. Virol. 81:1826–1830, 2009. © 2009 Wiley‐Liss, Inc.     

Molecular epidemiology of norovirus infections in sporadic cases of viral gastroenteritis among children in Northern Italy

Surveillance of norovirus infections in sporadic cases of pediatric gastroenteritis admitted to a main hospital in Northern Italy during a full-year period (2002) showed that noroviruses (10.4%) were the second most common causative viral agent, following rotaviruses (21.1%), and noroviruses (81%) were mostly implicated in mixed infections. The epidemic period of norovirus was September-December, with September and November as months of major prevalence (33.3 and 38.5%, respectively). Six distinct norovirus genotypes were detected (GI.7, GII.1, GII.2, GII.4, GII.7, GII, not assigned named GIIb), and the predominant genotype was GII.4. A "new GII.4 2002 variant" accounted for 82.9% of total strains. Since the severity of norovirus symptoms does not usually require admission to hospital, the burden of norovirus disease in the general children population may be much higher than that suggested by the present hospital-based investigation.     

河北省卢龙地区2008—2009年5岁以下腹泻住院儿童中诺如病毒的检测和分型

目的了解河北省卢龙地区2008—2009年5岁以下住院儿童中诺如病毒的分子流行病学特征。方法收集2008年10月至2009年8月325例5岁以下腹泻住院患儿粪便标本和流行病学资料,采用酶联免疫吸附试验（ELISA）检测轮状病毒抗原,利用多重RT．PCR方法检测诺如病毒,并对部分诺如病毒阳性株进行序列测定和系统进化分析。结果诺如病毒的检出率为11．3％（37／325）,仅次于轮状病毒的检出率（48．6％）,高于腺病毒（6．5％）和星状病毒（4．3％）,主要感染2岁以下儿童,季节高峰在11月,系统进化分析表明诺如病毒流行优势株为GII-4／2006b变异株,并发现一株未见报道的新型GII-4变异株。结论诺如病毒是引起2008—2009年卢龙地区的急性胃肠炎的重要病原之一,G114／2006b变异株仍是流行优势株,要进一步监测新型GII-4变异株的流行。     

Clinical features and molecular epidemiology of rotavirus and norovirus infections in Libyan children

Rotaviruses and noroviruses are leading viral causes of diarrhoea in children. A cross‐sectional study was undertaken among children aged <5 years with acute gastroenteritis at Al‐Jala Children's Hospital, Tripoli, Libya, from October 2007 to September 2008. Of 1,090 fecal samples collected, 260 from inpatients and 830 from outpatients, all inpatients and approximately a third of outpatients, selected systematically, were investigated for rotavirus and norovirus infection by ELISA and real‐time RT‐PCR, respectively. Of 520 fecal samples examined (inpatients = 260, outpatients = 260), 164 (31.5%) had rotavirus and 91 (17.5%) had norovirus detected. Rotavirus was identified more often among inpatients than outpatients (35.8% vs. 27.3% respectively, P = 0.038). Norovirus was detected more commonly among outpatients than inpatients (21.2% vs. 13.8% respectively, P = 0.028). The peak incidence of infection with both viruses was among children aged between 6 and 11 months. The number of rotavirus cases was highest between November and June with a peak detection rate of 50% in January. Norovirus occurred most commonly from May through August with a peak detection rate of 47% in August. The most prevalent rotavirus genotypes were P[8], G9 (n = 116, 65.9%), followed by P[8],G1 (n = 49, 27.8%); a single P[9], G3 strain was detected. There were seven distinct electropherotypes among the G9 strains and all belonged to VP7 Lineage III. Among 91 noroviruses identified, 90 were genogroup II. Of 26 genogroup II noroviruses examined, all were genotype GII.4. Rotaviruses and noroviruses are both important causes of gastrointestinal infection among young children in Libya. J. Med. Virol. 83:1849–1856, 2011. © 2011 Wiley‐Liss, Inc.