Molecular Epidemiology of Genogroup II Noroviruses Infection in Outpatients with Acute Gastroenteritis in Nanjing, China (2010–2013)

Abstract

Objective. Human noroviruses (NoVs) of genogroup II are the most common strains detected in sporadic cases of acute nonbacterial gastroenteritis in outpatients in Nanjing. To gain insight into the molecular epidemiology of GII strains, we analyzed 75 positive NoV cases from 2010 to 2013. Methods. The sporadic cases were detected by real-time PCR with specific primers and probes to human NoVs of genogroup I or II, human sapovirus, human rotavirus, human astrovirus, and human enteric adenovirus. Human NoVs of genogroup II were further studied by VP1 amplification (RT- PCR), cloning, sequencing, and phylogenetic analysis. Results. Rotavirus and human NoVs were more frequently detected in all the cases from 2010 to 2013. Human NoVs infection was more frequent since 2011 and more frequent than rotavirus infection after 2012. Out of the 75 NoV cases of genogroup II, there were 5 GII.6, 11 GII.3, and 59 GII.4. Of the 59 GII.4, 27 cases were previous GII.4.2006b strains that circulated between 2010 and 2012; while 32 cases were the newly emerging GII.4 strains GII.4.2012 from 2011 to 2013. Conclusion. Our data confirm other studies on the rapid emergence and displacement of highly virulent GII.4 strains.

Molecular Diversity of Sapovirus Infection in Outpatients Living in Nanjing, China (2011–2013)

“…Viral RNA was extracted as described in a previous paper [ 4 ]. For detecting human sapovirus, the primers and probe targeted a conserved region of the RNA polymerase [ 7 ], which was used in 25 μ L reaction volume with the Invitrogen Superscript III One-Step q-RT-PCR System in ABI 7500 FSAT SDS as described in a previous report [ 4 ]; the amplification results were determined, as in the same report [ 4 ].…”

“…The reaction was conducted with an initial RT step at 50°C for 30 mins, followed by PCR activation at 94°C for 2 mins and then 35 cycles of amplification (15 s at 94°C, 30 s at 48°C, and 30 s at 68°C) and a final extension step for 5 mins at 68°C in a GeneAmp PCR system 9700 thermal cycler (Applied Biosystems, Foster City, CA, USA). The RT-PCR products were purified, cloned, and sequenced as described in a previous report [ 4 ]; one direction sequencing entirely covered another direction.…”

“…All sequences generated in this study were edited and analyzed as noted in a previous report [ 4 ]. A phylogenetic tree was drawn with the software MEGA 5.0 [ 8 ].…”

“…Human calicivirus (HuCV) consists of noroviruses (NoVs) and sapovirus (SaV); they are important pathogens that are involved in nonbacterial acute gastroenteritis [ 1 – 3 ]. In a previous study our lab showed that HuCV has become the main pathogen of nonbacterial acute gastroenteritis in Nanjing after 2012 and replaced rotavirus as the predominant pathogen in 2013 [ 4 ].…”

Norovirus: the current focus on a major enteropathogen

“…As based on the sequencing analysis of VP1 (the major capsid protein) noroviruses have been assigned to five distinct genogroups (GI to GV) comprising at least 35 genetic clusters (or genotypes). Genogroups GI, GII and GIV are known to infect humans, with genotypes GII.4 and GI.1 (the prototype strain originally named Norwalk agent) being those more commonly identified 6 . Although numerous genotypes are known to infect humans, over the last decade GII.4 strains have remained dominant and are currently responsible for the majority of outbreaks that occur worldwide.…”