Molecular epidemiology and genotype distribution of noroviruses in children in Thailand from 2004 to 2010: A multi‐site study

Abstract

This study identified norovirus in children presenting with acute gastroenteritis and determined the capsid genotypes of the circulating norovirus strains in multiple regions in Thailand during October 2004 to December 2006 and March 2008 to August 2010. A total of 7,420 stool samples were collected from both cases (3621) and controls (3799). The stool samples were screened by two real-time RT-PCR assays to detect genogroup I and genogroup II noroviruses. Norovirus-positive samples were identified in 516 cases (14.3%) and 181 controls (4.8%) with more than half of norovirus positive samples from 7-24 months old children. Positive samples were sequenced and genotyped for the capsid gene. GII.4 was the genotype observed most frequently (56.4%) followed by GII.3 (28.2%). Five peaks of infection were observed, with predominant capsid genotypes that alternated during the surveillance periods between GII.4 and GII.3. Analyses of positive samples showed variation in genotype from each region as well as from different study periods. This emphasizes the importance of multi-site studies to investigate norovirus epidemiology. Additionally, the observed regional and temporal variations suggest that a systematic nation-wide surveillance effort in Thailand is needed to track the continually changing norovirus epidemiology.

Human norovirus genogroup II recombinants in Thailand, 2009–2014

“…In this study, *9 % of the stool samples obtained from children with diarrhea between 2009 and 2014 tested positive for GII NoVs. This rate was comparable to those found in other Thai studies [16]. Furthermore, GII.4 was the most common NoV genotype identified in this and many previous studies on stool samples done between 2002 and 2011 [19][20][21][22]27].…”

“…have generally been reported to be approximately 7-45 % [16], with a lower rate in adults [17] and higher rates in infants and young children [18][19][20][21][22]. Consistent with observations in other countries, most Thai studies found a predominance of GII noroviruses in the samples, especially GII.4 strains.…”

“…Despite the presence of NoV in patients with acute gastroenteritis and asymptomatic individuals [16,20], there are few published reports of NoV outbreaks in Thailand [26]. Incidence of diarrhea and the causative pathogens were often not investigated due to insufficient resources.…”

Monthly Distribution of Norovirus and Sapovirus Causing Viral Gastroenteritis in Thailand

“…In contrast, NoV GII was detected year-round in Thailand, although it was observed mainly in the dry and cool season, between September and February. Several reports have described the seasonality of NoV and SaV in Thailand (10)(11)(12). Bodhidatta et al (10) also reported clear peaks of NoV GII infections between October and February, corresponding to the dry and cool season.…”

“…A variety of NoV and SaV genotypes have been detected in Thailand (7,(10)(11)(12)15,16), while GII.4 has been reported to be remarkably predominant in Thailand, as were as worldwide. In this study, all of the randomly selected samples were GII.…”