Norovirus Epidemiology in Africa: A Review

Surveillance of norovirus among children with diarrhea in four major hospitals in Bhutan: Replacement of GII.21 by GII.3 as a dominant genotype

Background

Diarrhea is a major cause of morbidity and mortality among Bhutanese children. The etiology of diarrhea is not well known due to the challenges of conducting routine surveillance with Bhutan’s modest research facilities. Establishing an etiology is crucial toward generating evidence that will contribute to policy discussions on a diarrheal disease control program. Our previous study, during 2010–2012, revealed that norovirus (NoV) is an important cause of diarrhea among Bhutanese children, and that GII.21 was the major genotype circulating at that time. In other countries, GII.4 is the major genotype responsible for NoV infections. In this update report, we provide new prevalence data to describe the progression of the transformation and distribution of the NoV genotype among Bhutanese children.

Methods

From June 2013 through May 2014, diarrheal stool samples were collected at one national referral hospital in Thimphu, two regional referral hospitals in the eastern and central regions, and one general hospital in the western region of Bhutan. NoV was detected by reverse transcription–polymerase chain reaction (RT–PCR), by amplifying the capsid gene. The RT–PCR results were confirmed by nucleotide sequencing of the amplicons.

Results

The proportion of NoV-positive stool samples was 23.6% (147/623), of which 76.9% were NoV GII and the remainders were NoV GI. The median age of infected children was 15.5 months, with a fairly balanced female: male ratio. NoV GII was most prevalent in the colder months (late November–mid April) and NoV GI had the highest prevalence in the summer (mid April–late September). Nucleotide sequencing was successful in 99 samples of GII strains. The most common genotypes were GII.3 (42.6%), GII.4 Sydney 2012 (15.8%), and GII.4 unassigned (11.9%). No GII.21 was found in any child in the present study. Phylogenetic analysis showed that GII.3 strains in the present study belonged to an independent cluster in lineage B. These strains shared an ancestor with those from different countries and Bhutanese strains circulating during 2010.

Conclusion

NoV remains an important cause of diarrhea among Bhutanese children. Genotype GII.3 from a single ancestor strain has spread, replacing the previously circulating GII.21. Current NoV genotypes are similar to the strains circulating worldwide but are primarily related to those in neighboring countries. NoV GII is prevalent during the cold season, while GI is prevalent during the summer. To develop a NoV infection control policy, further studies are needed.

High prevalence of norovirus in children with sporadic acute gastroenteritis in Manaus, Amazon Region, northern Brazil

BACKGROUND

Norovirus (NoV) is a major cause of acute gastroenteritis (AGE) worldwide, especially in children under five years. Studies involving the detection and molecular characterisation of NoV have been performed in Brazil, demonstrating its importance as an etiological agent of AGE.

OBJECTIVES

The objectives of this study were to investigate the frequency of human NoV and to genotype the strains isolated from 0-14-year-old patients of AGE in Manaus, Brazil, over a period of two years.

METHODS

A total of 426 faecal samples were collected between January 2010 and December 2011. All samples were tested for the presence of NoV antigens using a commercial enzyme immunoassay kit. RNA was extracted from all faecal suspensions and reverse transcription-polymerase chain reaction (RT-PCR) for the NoV-polymerase partial region was performed as a trial test. Positive samples were then subjected to PCR with specific primers for partial capsid genes, which were then sequenced.

FINDINGS

NoV was detected in 150 (35.2%) faecal samples, for at least one of the two techniques used. NoV was detected in children from all age groups, with the highest positivity observed among the group of 1-2 years old. Clinically, fever was verified in 43% of the positive cases and 46.3% of the negative cases, and vomiting was observed in 75.8% and 70.8% cases in these groups, respectively. Monthly distribution showed that the highest positivity was observed in January 2010 (81.2%), followed by February and April 2010 and March 2011, when the positivity rate reached almost 50%. Phylogenetic analyses performed with 65 positive strains demonstrated that 58 (89.2%) cases of NoV belonged to genotype GII.4, five (7.7%) to GII.6, and one (1.5%) each to GII.7 and GII.3.

MAIN CONCLUSIONS

This research revealed a high circulation of NoV GII.4 in Manaus and contributed to the understanding of the importance of this virus in the aetiology of AGE cases, especially in a region with such few studies available.

Quantification of multiple waterborne pathogens in drinking water, drainage channels, and surface water in Kampala, Uganda, during seasonal variation

Longitudinal water quality monitoring is important for understanding seasonal variations in water quality, waterborne disease transmission, and future implications for climate change and public health. In this study, microfluidic quantitative polymerase chain reaction (MFQPCR) was used to quantify genes from pathogens commonly associated with human intestinal infections in water collected from protected springs, a public tap, drainage channels, and surface water in Kampala, Uganda, from November 2014 to May 2015. The differences in relative abundance of genes during the wet and dry seasons were also assessed. All water sources tested contained multiple genes from pathogenic microorganisms, with drainage channels and surface waters containing a higher abundance of genes as compared to protected spring and the public tap water. Genes detected represented the presence of enterohemorrhagic Escherichia coli, Shigella spp., Salmonella spp., Vibrio cholerae, and enterovirus. There was an increased presence of pathogenic genes in drainage channels during the wet season when compared to the dry season. In contrast, surface water and drinking water sources contained little seasonal variation in the quantity of microbes assayed. These results suggest that individual water source types respond uniquely to seasonal variability and that human interaction with contaminated drainage waters, rather than direct ingestion of contaminated water, may be a more important contributor to waterborne disease transmission. Furthermore, future work in monitoring seasonal variations in water quality should focus on understanding the baseline influences of any one particular water source given their unique complexities.

Genetic characterisation of Norovirus strains in outpatient children from rural communities of Vhembe district/South Africa, 2014-2015

BACKGROUND

Norovirus (NoV) is now the most common cause of both outbreaks and sporadic non-bacterial gastroenteritis worldwide. However, data supporting the role of NoV in diarrheal disease are limited in the African continent.

OBJECTIVES

This study investigates the distribution of NoV genotypes circulating in outpatient children from rural communities of Vhembe district/South Africa.

STUDY DESIGN

Stool specimens were collected from children under five years of age with diarrhea, and controls without diarrhea, between July 2014 and April 2015. NoV-positive samples, detected previously by Realtime PCR, were analysed using conventional RT-PCR targeting the partial capsid and polymerase genes. Nucleotide sequencing methods were performed to genotype the strains.

RESULTS

The sequence analyses demonstrated multiple NoV genotypes including GI.4 (13.8%), GI.5 (6.9%), GII.14 (6.9%), GII.4 (31%), GII.6 (3.4%), GII.P15 (3.4%), GII.P21 (3.4%) and GII.Pe (31%). The most prevalent NoV genotypes were GII.4 Sydney 2012 variants (n=7) among the capsid genotypes, GII.Pe (n=9) among the polymerase genotypes and GII.Pe/GII.4 Sydney 2012 (n=8) putative recombinants among the RdRp/Capsid genotypes. Two unassigned GII.4 variants were found.

CONCLUSIONS

The findings highlighted NoV genetic diversity and revealed continuous pandemic spread and predominance of GII.Pe/GII.4 Sydney 2012, indicative of increased NoV activity. An unusual RdRp genotype GII.P15 and two unassigned GII.4 variants were also identified from rural settings of the Vhembe district/South Africa. NoV surveillance is warranted to help to inform investigations into NoV evolution and disease burden, and to support on-going vaccine development programmes.

Norovirus epidemiology in South African children <5 years hospitalised for diarrhoeal illness between 2009 and 2013

Public health interest in norovirus (NoV) has increased in recent years following improved diagnostics, global burden estimates and the development of NoV vaccine candidates. This study aimed to describe the detection rate, clinical characteristics and environmental features associated with NoV detection in hospitalized children <5 years with diarrhoea in South Africa (SA). Between 2009 and 2013, prospective diarrhoeal surveillance was conducted at four sites in SA. Stool specimens were collected and screened for NoVs and other enteric pathogens using molecular and serological assays. Epidemiological and clinical data were compared in patients with or without detection of NoV. The study detected NoV in 15% (452/3103) of hospitalized children <5 years with diarrhoea with the majority of disease in children <2 years (92%; 417/452). NoV-positive children were more likely to present with diarrhoea and vomiting (odds ratio (OR) 1·3; 95% confidence interval (CI) 1·1-1·7; P = 0·011) with none-to-mild dehydration (adjusted OR 0·5; 95% CI 0·3-0·7) compared with NoV-negative children. Amongst children testing NoV positive, HIV-infected children were more likely to have prolonged hospitalization and increased mortality compared with HIV-uninfected children. Continued surveillance will be important to consider the epidemic trends and estimate the burden and risk of NoV infection in SA.

A Rapid Epidemiological Tool to Measure the Burden of Norovirus Infection and Disease in Resource-Limited Settings

Background

Rapid, cost-effective tools are needed to estimate the disease burden of acute gastroenteritis (AGE) and norovirus (NoV) in resource-limited settings.

Methods

Households with children (6 weeks–17 years) in rural Guatemala were randomly enrolled into 2 parallel AGE surveillance systems: (1) a prospective cohort, which included an enrollment visit followed by 1 year of prospective observation using a smartphone-based weekly symptom diary; and (2) 2 sequential cross-sectional rapid active sampling (RAS) surveys. Norovirus testing was performed during enrollment (all subjects) and for prospective AGE episodes (prospective cohort only).

Results

The prospective cohort enrolled 207 households (469 children) from April to September 2015 followed by 471 person-years of observation; RAS survey 1 enrolled 210 households (402 children) during October to November 2015, and RAS survey 2 enrolled 210 separate households (368 children) during January to February 2016. The prospective cohort detected a NoV+ AGE prevalence of 11% and a population-attributable fraction (PAF) of −1.6% at enrollment, followed by an incidence of 1.4 episodes/100 person-years. Rapid active sampling surveys 1 and 2 identified a NoV+ AGE prevalence of 14%–21% and a PAF of 3.2%–12.4%.

Conclusions

Rapid active sampling surveys were practical and identified more cases of NoV infection and disease compared with a parallel prospective cohort in rural Guatemala.

The Vast and Varied Global Burden of Norovirus: Prospects for Prevention and Control

Globally, norovirus is associated with approximately one-fifth of all diarrhea cases, with similar prevalence in both children and adults, and is estimated to cause over 200,000 deaths annually in developing countries. Norovirus is an important pathogen in a number of high-priority domains: it is the most common cause of diarrheal episodes globally, the principal cause of foodborne disease outbreaks in the United States, a key health care-acquired infection, a common cause of travel-associated diarrhea, and a bane for deployed military troops. Partly as a result of this ubiquity and burden across a range of different populations, identifying target groups and strategies for intervention has been challenging. And, on top of the breadth of this public health problem, there remain important gaps in scientific knowledge regarding norovirus, especially with respect to disease in low-income settings. Many pathogens can cause acute gastroenteritis. Historically, rotavirus was the most common cause of severe disease in young children globally. Now, vaccines are available for rotavirus and are universally recommended by the World Health Organization. In countries with effective rotavirus vaccination programs, disease due to that pathogen has decreased markedly, but norovirus persists and is now the most common cause of pediatric gastroenteritis requiring medical attention. However, the data supporting the precise role of norovirus in low- and middle-income settings are sparse. With vaccines in the pipeline, addressing these and other important knowledge gaps is increasingly pressing. We assembled an expert group to assess the evidence for the global burden of norovirus and to consider the prospects for norovirus vaccine development. The group assessed the evidence in the areas of burden of disease, epidemiology, diagnostics, disease attribution, acquired immunity, and innate susceptibility, and the group considered how to bring norovirus vaccines from their current state of development to a viable product that will benefit global health.