Noroviruses are a leading cause of acute sporadic gastroenteritis worldwide. In Sub-Saharan Africa, information regarding norovirus infections in children is scarce. A systematic review of studies performed between 1993 and June 2015 was conducted to establish the genotypic distribution and prevalence of norovirus infections in children (≤17) in Sub-Saharan Africa. Analysis of data from 19 studies involving 8,399 samples from children with symptomatic and nonsymptomatic gastroenteritis revealed prevalence of 12.6% (range 4.6% to 32.4%). The prevalence of norovirus infections was higher in symptomatic children (14.2%) than asymptomatic children (9.2%). Genogroup II (GII) was the most prevalent genogroup accounting for 76.4% of all the reported norovirus infections. The rest of the infections were GI (21.7%) and GI/GII (1.9%). The most common genotypes were GII.4 (65.2%), GI.7 (33.3%), and GI.3 (21.3%). These statistics were calculated from studies carried out in 12 out of 48 Sub-Saharan African countries. Therefore, more studies involving several countries are required to determine fully the epidemiology of noroviruses and their contribution to childhood diarrhoea in Sub-Saharan Africa.
Acute gastroenteritis is a common illness which is debilitating and life-threatening in children younger than five years of age [
Noroviruses have a linear and polyadenylated genome surrounded by nonenveloped, icosahedral capsid of 27 to 40 nm in diameter [
Acute norovirus infection is characterised by nonspecific symptoms such as vomiting, nausea, abdominal cramps, myalgias, and intense watery nonbloody diarrhoea that commonly resolves in 2-3 days [
A systematic scientific literature review of norovirus studies in Sub-Saharan Africa published in peer reviewed journals in electronic databases such as PubMed, Medline, Scopus, and Google Scholar from 1993 to June 2015 was performed using keywords such as “gastroenteritis”, “children”, “norovirus”, “Africa”, and “name of country” alone and in various combinations. To avoid leaving out any studies that were not available in major scientific databases or nonindexed journals, Google search was also used. Master of Science theses whose contents have not been published in any journal were also included in the review. Studies outside Sub-Saharan Africa and those involving adult participants alone were excluded. For studies involving both children and adults, only data from children was extracted and included in this review. All studies describing norovirus infections in symptomatic and asymptomatic children were included. Due to the scarcity of information on norovirus infections in children in Sub-Saharan Africa, studies of all durations (≥1 month) were included in this systematic review.
When reviewing the studies, frequencies of genogroup I and of genogroup II genotypes were calculated independently. Classification of genotypes into polymerase and capsid genotypes was not considered in the analysis due to lack of information. To calculate the approximate prevalence of norovirus infections in Sub-Saharan Africa, only reverse transcription PCR based studies were included. However, a reverse transcription PCR based study by Wolfaardt et al. that used calicivirus positive samples only to calculate the prevalence of Norwalk virus in South Africa was excluded from the calculation [
Thirty-five studies were identified in Africa and only 23 were in Sub-Saharan Africa [
In Sub-Saharan Africa, norovirus associated gastroenteritis outbreaks were first reported in South Africa in 1993 [
Norovirus infections in children in Sub-Saharan Africa.
Country | Prevalence of norovirus (%) | Sample size | Year of samples collected | Age (years) | Reference | |||
---|---|---|---|---|---|---|---|---|
Total | GI | GII | GI/GII | |||||
Botswana | 24 | 3 | 21 | 0 | 100 | 2000–2006 | ≤1–≥3 | [ |
Cameroon | 29.6 | 12.9 | 16.7 | 0 | 54 | Oct–Dec 2009 | 5–15 | [ |
Cameroon | 4.6 | 2.2 | 2.4 | 0 | 146 (1244 samples) | Sep 2011–Aug 2012 | 1–17 | [ |
Malawi | 11.3 | 1.8 | 9.4 | 0.1 | 1941 | July 1997–June 2007 | <5 | [ |
Tanzania | 13.7 | — | — | — | 270 | Dec 2005–Feb 2006 | <5 | [ |
Tanzania | 14.3 | 0.9 | 13.3 | 0.1 | 1266 | 2010-2011 | ≤2 | [ |
Ghana | 15.9 | 3.7 | 12.2 | 0 | 82 | Aug 1998–July 2000 | ≤2 | [ |
Ghana | 16.4 | 1.3 | 15.1 | 0 | 152 | Feb 2011–Feb 2012 | ≤5 | [ |
Ghana | 7.4 | 1.4 | 6 | 0 | 367 | Nov 2005–Jan 2006 | ≤11 | [ |
Nigeria | 25.5 | 1.8 | 23.6 | 0 | 55 | June 2010–Jan 2011 | ≤5 | [ |
Nigeria |
32.4 | 2.6 | 4.3 | 1.6 | 100 | Nov 2007–Jan 2008 | <5 | [ |
Burkina Faso | 22.2 | 8.8 | 10.5 | 2.9 | 418 | Nov 2005–Jan 2007 | ≤10 | [ |
Burkina Faso | 12 | 2.3 | 9.7 | — | 309 | May 2009–Mar 2010 | <5 | [ |
Kenya | 6.3 | — | — | — | 206 | Jan 2007–June 2010 | <14 | [ |
Madagascar | 5.9 | 1.7 | 4.2 | 0 | 237 | Nov 2005–Jan 2008 | ≤16 | [ |
Rwanda | 11 | 3.8 | 7.2 | 0 | 706 | Nov 2009–June 2012 | ≤5 | [ |
South Africa | 14.3 | 1.2 | 12.7 | 0.4 | 245 | Jan–Dec 2008 | ≤13 | [ |
Gabon | 23 | 9.1 | 13.9 | 0 | 317 | Mar 2010–June 2011 | <5 | [ |
Tanzania (Zanzibar) | 11.8 | 0.6 | 11.2 | 0 | 330 | April–July, 2011 | <5 | [ |
Countries where norovirus infections in children have been reported in Sub-Saharan Africa. Countries with high norovirus prevalence (>20% ≤32.4%) are represented by the red colour. Yellow: countries with norovirus prevalence between 10% and 20%. Light green: countries with less than 10% norovirus prevalence. At the time of writing this review, there were no published reports about prevalence rates of norovirus infections in
Four studies, from South Africa, Nigeria, Malawi, and Gabon, clearly reported the occurrence of noroviruses in diarrhoea samples as single or mixed infections [
GII was the most common genogroup accounting for 76.4% (730/955) of all the reported norovirus infections from 17 studies in Sub-Saharan Africa. Two studies had no information on the genogroups and one study from Nigeria (included in the 17 studies) did not sequence all the norovirus positive samples to determine the genogroups [
Distribution of GI and GII norovirus genotypes (capsid and polymerase combined) in Sub-Saharan Africa. (a) Relative frequencies of GI genotypes among a total of 42 GI norovirus positive samples from nine studies. GI.7 and GI.3 norovirus infections were more common than any other GI genotype. (b) Relative frequencies of GII genotypes among a total of 368 GII norovirus positive samples from nine studies. GII.4 (65.2%) was the most prevalent genotype. Und: undefined. Rest: GII.e, GII.8, GII.11, GII.13, GII.14, and GII.15.
Norovirus recombinants were only reported in four studies in Burkina Faso, Madagascar, Ghana, and South Africa [
Norovirus infections were less prevalent in Burkinabe children with blood group A (Odds Ratio 0.31;
Three smaller studies in Tanzania, South Africa, and Cameroon reported the prevalence of norovirus infections in HIV positive people [
The seasonal distribution of noroviruses varied between different Sub-Saharan African countries. In South Africa and Madagascar, norovirus detection peaked in November and December 2008 while Malawi had two peak norovirus seasons, August to November and February to March between 1997 and 2007 [
Data from this review shows that the prevalence (12.6%) of norovirus infections in children in Sub-Saharan Africa is higher than previously thought. In most of the studies included in this review, the prevalence of norovirus was higher in the cases than in the controls [
Generally, most of the studies included in this review had smaller sample sizes. Only three studies had sample sizes above 1000 [
Additionally, the duration of many of the studies was less than 12 months, and hence results from such studies are but just an eye-opener of the role of noroviruses in childhood diarrhoea in those countries [
Although the prevalence of norovirus infections is approximately 12.6% in Sub-Saharan Africa, the contribution of noroviruses to acute and chronic diarrhoea in this subregion is still obscure.
Detection of norovirus in a stool sample from a child with gastroenteritis does not always mean that this is the cause; there may be mixed infections with other bacterial and viral agents. As true as this statement may sound, many studies included in this review did not investigate the occurrence of noroviruses as single or mixed virus infections in norovirus positive diarrhoea samples. For studies, such as those conducted in South Africa, Nigeria, and Malawi, that investigated occurrence of noroviruses as single or mixed infections with other viral pathogens, they did not investigate coinfections with protozoal and bacterial agents [
Out of a total of 19 studies that were included in this review, only 9 had information of the prevalence of GI and GII genotypes, representing a total of 368 GII genotypes and 42 GI genotypes. This, coupled with smaller sample sizes and fewer studies, makes the distribution of norovirus genotypes highlighted in this review unrepresentative of actual norovirus genotypes that may be circulating in Sub-Saharan Africa [
Noroviruses have been shown to cause chronic and persistent gastroenteritis in immunocompromised individuals such as HIV/AIDs patients, lasting several weeks to years [
Whilst all the studies included in this systematic review provided evidence on the prevalence of norovirus infections in children in Sub-Saharan Africa, none of them critically looked at the possible risk factors and transmission dynamics of noroviruses. It would be worthwhile to investigate the transmission dynamics and risk factors associated with norovirus infections in Sub-Saharan Africa.
The prevalence of norovirus infections in children with symptomatic and nonsymptomatic gastroenteritis in Sub-Saharan Africa is approximately 12.6%. However, most of the studies from which this figure was derived had small sample sizes and were of a shorter duration. It is therefore prudent that the epidemiology of noroviruses and their contribution to childhood diarrhoea and deaths in Sub-Saharan Africa should be investigated further using large scale longitudinal studies.
The findings and conclusions in this report are those of the author.
The author declares no competing interests.
The author thanks Dr. Benjamin Mubemba for assisting with editing the paper.