Abrupt emergence and predominance in Vietnam of rotavirus A strains possessing a bovine-like G8 on a DS-1-like background.

An apparently single rotavirus A strain possessing a genotype constellation of G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 abruptly emerged, caused diarrhoea in children requiring hospitalisation, and increased to reach 27 % of strains detected during the first half of 2015 in Vietnam.

Molecular epidemiology of noroviruses detected in Vietnamese children with acute gastroenteritis from 2012 to 2015.

Noroviruses, an important cause of diarrhoea in humans, are genetically diverse. The recent norovirus seasons recorded the emergence of new recombinants of the capsid and polymerase genotypes, with a global dominance of GII.Pe_GII.4 Sydney 2012 and GII.P17_GII.17 in Asian countries. However, the number of papers reporting the distribution of both polymerase and capsid genotypes circulating among children is scarce, with none from Vietnam. This study described both the polymerase and capsid genotypes of noroviruses circulating in Vietnamese children using stool specimens obtained under the World Health Organization rotavirus surveillance programme from 2012 to 2015. Of 350 specimens tested, noroviruses were detected in 90 (28 %) of 319 inpatient specimens and in 9 (29 %) of 31 outpatient specimens. The polymerase and capsid genotype combinations of GII.Pe_GII.4 Sydney 2012 and GII.P21_GII.3 were co-dominant (51 and 24 %, respectively), both of which were recombinants, contributing to a high proportion (87 %) of recombinants among circulating noroviruses. GII.4 variants evolved in the same fashion in Vietnam as in other countries, with amino acid substitutions in the putative variant-specific epitopes of the protruding domain. Unlike neighbouring countries where the predominance of GII.P17_GII.17 was reported, only one GII.P17_GII.17 strain was detected from an outpatient in 2015 in Vietnam. In conclusion, a substantial burden due to norovirus gastroenteritis hospitalizations among Vietnamese children was associated with circulating co-dominant GII.Pe_GII.4 Sydney 2012 and GII.P21_GII.3 strains. Continued surveillance is necessary to monitor infection caused by GII.4 variants and that of GII.P17_GII.17 noroviruses in paediatric patients in Vietnam.

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.