Isolated norovirus GII.7 strain within an extended GII.4 outbreak

Prevalence and genetic diversity of norovirus genogroup II in children less than 5 years of age with acute gastroenteritis in Tehran, Iran

Viral gastroenteritis is a major public health problem worldwide. In Iran, very limited studies have been performed with regard to the epidemiology of noroviruses. This study aimed to evaluate the prevalence and molecular epidemiology of GII noroviruses in hospitalized children less than 5 years of age with acute gastroenteritis (AGE). A total of 210 stool specimens were collected from Ali Asghar Children's Hospital and Bahrami Children's Hospital in Tehran, from June 2015 to June 2016. The samples were screened by real-time RT-PCR for genogroup II (GII). Positive samples were genotyped by semi-nested PCR followed by Sanger sequencing and phylogenetic analysis. Norovirus was identified in 36 (17.1%) of 210 specimens. Based on genetic analysis of RdRp and capsid sequences, the strains were clustered into eight RdRp-capsid genotypes: GII.P4-GII.4 Sydney_2012 (41.7%), GII.Pe-GII.4 Sydney_2012 (30.6%), GII.P21-GII.3 (13.9%), GII.P16-GII.4 Sydney_2012 (2.8%), GII.P16-GII.12 (2.8%), GII.P2-GII.4 Sydney_2012 (2.8%), GII.P7-GII.7 (2.8%) and GII.P2-GII.2 (2.8%). We determined several different co-circulating norovirus genotypes in children < 5 years of age with AGE in our hospital in Tehran, Iran. Continued molecular surveillance of noroviruses, including typing of both RdRp and capsid genes, is important for monitoring emerging strains in our continued efforts to reduce the overall burden of norovirus disease.

Use of ward closure to control outbreaks among hospitalized patients in acute care settings: a systematic review

BACKGROUND

Though often used to control outbreaks, the efficacy of ward closure is unclear. This systematic review sought to identify studies defining and describing ward closure in outbreak control and to determine impact of ward closure as an intervention on outbreak containment.

METHODS

We searched these databases with no language restrictions: MEDLINE, 1946 to 7 July 2014; EMBASE, 1974 to 7 July 2014; CINAHL, 1937 to 8 July 2014; and Cochrane Database of Systematic Reviews, 2005 to May 2014. We also searched the following: IndMED; LILACS; reference lists from retrieved articles; conference proceedings; and websites of the CDCP, the ICID, and the WHO. We included studies of patients hospitalized in acute care facilities; used ward closure as a control measure; used other control measures; and discussed control of the outbreak(s) under investigation. A component approach was used to assess study quality.

RESULTS

We included 97 English and non-English observational studies. None included a controlled comparison between ward closure and other interventions. We found that ward closure was often used as part of a bundle of interventions but could not determine its direct impact separate from all the other interventions whether used in parallel or in sequence with other interventions. We also found no universal definition of ward closure which was widely accepted.

CONCLUSIONS

With no published controlled studies identified, ward closure for control of outbreaks remains an intervention that is not evidence based and healthcare personnel will need to continue to balance the competing risks associated with its use, taking into consideration the nature of the outbreak, the type of pathogen and its virulence, mode of transmission, and the setting in which it occurs. Our review has identified a major research gap in this area.

Different norovirus genotypes in patients with gastroenteritis in Kuwait

Norovirus is a leading cause of acute gastroenteritis worldwide. The importance of this virus infection in Kuwait is not known. Eight out of 100 stool samples (8.0%) from children up to 5 years of age with gastroenteritis studied during 2006-2007 from one hospital, and 6 out of 70 stool samples (8.5%) from similar children studied from another hospital during 2010-2011 were positive for norovirus by RT-PCR. Out of these 170 samples studied from both hospitals, 10 samples were positive for norovirus when tested by ELISA. Phylogenetic tree analysis of norovirus strains showed that 50% of the norovirus strains belonged to genotype GII.4, and the predominant strain was GII.4 2006b. Other detected genotypes were GII.12, GII.b, GII.3, GII.8, and GII.7. This study highlights the importance of screening for norovirus infection in acute gastroenteritis and having a reporting system to understand better the epidemiology of norovirus infection in Kuwait.

New norovirus classified as a recombinant GII.g/GII.1 causes an extended foodborne outbreak at a university hospital in Munich

BACKGROUND

Noroviruses are among the most prevalent causative agents for gastroenteritis worldwide. The low infectious dose, its stability in the environment, and its genetic variability enable the virus to cause outbreaks, especially in health care facilities and other similar settings. Genotype II.4 has been most prevalent over the last years.

OBJECTIVES

To characterize an extended norovirus outbreak at a university hospital in Munich, Germany, molecularly and epidemiologically.

STUDY DESIGN

The outbreak affecting more than 100 persons within 3 days was monitored by real time PCR. The rapid onset indicated a food-borne outbreak. Rigorous hygienic measures, including disinfection procedures and closure of wards helped contain the outbreak within 6 days. A 2193 nt sequence covering polymerase (825 nt) and capsid gene (1388 nt) was characterized from 4 specimens derived from different wards and the catering facility.

RESULTS

Our polymerase sequences were classified GII.g, whereas the capsid belonged to GII.1. Recombination analysis revealed a putative breakpoint at a typical location. Our sequenced region clustered with GIIg/GII.1 sequences first detected in Hungary, Belgium, and the US in 2010. p-Distances on nucleic acid level were 0.18 and 0.21, respectively.

CONCLUSIONS

Our data establish a novel strain classified as GII.g/GII.1 as the causative agent for an extended outbreak.

Molecular characterization of human calicivirus associated with acute diarrheal disease in Mexican children

Background

Human caliciviruses (HuCV) are emerging enteric pathogens that are a common cause of diarrhea in humans worldwide. Due to the paucity of information on the molecular characterization of HuCV circulating in Mexico, the aim of this work was to investigate the diversity and molecular epidemiology of the HuCV infection associated with acute diarrheal disease in Mexican children aged up to 5 years.

Results

Of the 131/414 (32%) HuCV positive-specimens analyzed, 128 were identified as Norovirus (NoV) and three as Sapovirus (SaV). Of the NoV positive specimens, 118/128 (92%) were NoV GII and 10/128(8%) were untypeable by RT-PCR in both polymerase and capsid genes, whereas one SaV isolate was further confirmed by sequencing as GI.2. Phylogenetic analysis based on polymerase partial gene sequences from 89/131 (68%) HuCV isolates showed that 86/89 (97%) belong to NoV GII.4 with three main variant clusters of this genotype, 2/89 (2%) to NoV GII.2, and 1/89 (1%) to SaV GI.2. Furthermore, partial sequencing of the capsid gene VP1 of 63/131 (48%) strains indicated that 61/63 (97%) correlated with NoV GII.4, whereas only 2/63 (3%) clustered to NoV GII.2. HuCV infections were detected throughout the year, and the highest number of cases positive for NoV was found in children between 7 and 18 months of age (60%).

Conclusions

This study highlights the usefulness of analyzing both polymerase and capsid genes for molecular characterization of HuCV and demonstrates the relatedness and predominance of NoV GII.4 with acute diarrheal disease in young Mexican children, thus contributing to better understanding of the molecular epidemiology of this disease.

Norovirus GII.4 and GII.7 capsid sequences undergo positive selection in chronically infected patients

Norovirus has become an important cause for infectious gastroenteritis. Particularly genotype II.4 (GII.4) has been shown to spread rapidly and causes worldwide pandemics. Emerging new strains evade population immunity and lead to high norovirus prevalence. Chronic infections have been described recently and will become more prevalent with increasing numbers of immunocompromized patients. Here, we studied norovirus evolution in three chronically infected patients, two genotypes II.4 and one II.7. A 719 and 757 nt region was analyzed for GII.4 and GII.7, respectively. This covers the entire hypervariable P2 domain of the VP1 capsid gene. Genetic variability at given and between different time points was assessed. Evolutionary adaptation was analyzed by Bayesian sampling of genealogies. This analysis clearly demonstrated positive selection rather than incidental drift for all three strains. The GII.7 and one GII.4 strain accumulated on average 5-9 mutations per 100 days, most of them non-synonymous. This is a much higher evolutionary rate than observed for noroviruses on a global level. Our data demonstrate that norovirus quasispecies are positively selected in chronically infected patients. The numbers of intraindividual amino acid mutations acquired in the capsid gene are similar to those separating consecutive GII.4 epidemic strains. Evolution in a given, chronically infected individual may thus generate novel genotypes at risk to expedite global evolution particularly for slowly evolving genotypes, as GII.7.