Introduction

Acute lower respiratory tract infections (ALRTIs) are infections in the trachea, lungs, bronchi, bronchioles, and alveoli [1]. Common ALRTIs usually include pneumonia, bronchitis and bronchiolitis [1]. ALRTIs are the leading cause of diseases and deaths among children under 5 years globally [2, 3]. It is worth noting that about 97% of all cases of ALRTIs are reported in low-and middle-income countries (LMICs), with most cases (about 70%) coming from South Asia and sub-Saharan Africa [SSA] [4]. Pneumonia kills more children than any other infectious disease, accounting for over 800,000 mortalities in children under 5 years annually [4]. Thus, each day about 2,200 children under five die of pneumonia. The highest deaths come from South Asia (2,500 cases per 100,000 children under five) and SSA (1,620 cases per 100,000 children under five). Unfortunately, all these deaths could have been prevented [1]. Data from UNICEF shows that progress in reducing pneumonia deaths in children under five has been significantly slower than in other infectious diseases such as diarrhoea, sepsis and malaria, especially in resource-poor settings like SSA [4].

The pathogens that cause ALRTIs vary depending on the person’s age [5]. Streptococcus pyogenes, Pneumococci, Staphylococcus aureus, Klebsiella pneumonia, and Haemophilus influenzae are the known causes of bacterial ALRTIs among children under 5 years of age [5, 6]. In addition, respiratory syncytial virus (RSV), parainfluenza type 3 virus (PF3), adenovirus (Adeno), influenza virus (FLU), and enterovirus are the common viruses that cause ALRTIs in children under 5 years of age [6]. Antibiotics are effective against most bacterial infections. However, evidence shows that diversity of the organisms causing ALRTIs and the deficit (about 30%) in diagnosis makes its management and treatment among children challenging [6]. Perhaps, these treatment challenges might be the reason for slower than expected reduction in ALRTIs among under five [4]. Hence, one of the best ways of achieving a significant reduction in morbidities and mortalities associated with ALRTIs among under five children is prevention of the disease through disruption of transmission of pathogens and reduction in risk factors.

The evidence further shows that several factors are linked to ALRTIs among children under 5 years [7]. However, Seidu and colleagues argued that there might be variations in these factors in LMICS and high-income countries [6]. This means that effective policies and strategies developed based on risk factors in high-resourced countries for preventing ALRTIs among children under five might not be effective in preventing the same among population in low-resourced countries, especially countries in SSA. Hence, it is important to identify the risk factors for ALRTIs, which are pertinent for developing effective policies and interventions to interrupt the transmission of ALRTIs pathogens and to ensure improved health outcomes.

For decades of research into ALRTIs, reviews mapping the prevalence, risk factors and interventions for ALRTIs among children under 5 years in SSA are scarce.. Some reviews considered pathogens [8] and air pollution as risk factors for ALRTIs among children under 5 years [9]. Therefore, this scoping review aims to map evidence on the prevalence and risk factors of ALRTIs among children under 5 years in SSA to inform future studies and help develop robust and effective policies and interventions in the prevention and protection of children under 5 years from infection. Perhaps, prevention becomes the best and most cost-effective strategy for protecting children under 5 years of age from ALRTIs since countries in SSA are already facing challenges in health systems, diagnosis and treatment of ALRTIs [6, 8, 10].

Methods

This scoping review adopted the guidelines of Arksey and O’Malley [11]. We also adopted the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist [12]. Three research questions guided this review: (1) what is the prevalence of reported ALRTIs among children under 5 years in SSA? (2) what are the risk factors of ALRTIS among children under 5 years in SSA? and (3) what interventions serve as protective factors for children under five in SSA against ALRTIs?

To get relevant studies for this review, the authors developed eligibility criteria. Table 1 presents the search strategy and the eligibility criteria. The search was conducted in four main databases (PubMed, JSTOR, Central, and Web of Science). An initial search was conducted in PubMed using Medical Subject Headings (MeSH) and later adapted to other databases. A chartered librarian, Dr Kwame Kodua-Ntim, at the Sam Jonah Library was consulted for records search and data management. Additional sources such as The WHO Library, Maternal Surveillance and Response Action Network, Google Scholar, Google, Z-library, HINARI, and institutional repositories of some universities in SSA were searched for relevant records. Mendeley software was used to remove duplicates and manage records during the screening process. All authors were involved in the screening for relevant records for this review. The reference lists of eligible studies were checked to identify relevant papers for this review.

Table 1 Search strategy for articles on ALRTIs among children under five in SSA
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To ensure accuracy and consistency in our approach to this review, two groups of authors (TBG, A-GO, and PYK; AKA and IA) independently extracted the data. Discrepancies during data charting were resolved during regular meetings by all the authors. The data charting process was supervised and reviewed by JOS and MA. In addition, EWA (Health Promotion expert), FA-M (Medical expert and Consultant General Surgeon), and PO-A (Paediatric Nurse Specialist) served as independent subjects and review experts that guided the entire review process. The analysis involved thematic and content analysis.

Results

The search was done in the main four databases (PubMed, Central, Web of Science and JSTOR) and produced 3,301 records. In addition, 28 records were ascertained from searches in other sources such as google, Z-library.org, institutional repositories, and google scholar. After the removal of 362 duplicates, 2,967 records were further screened. Finally, 94 full-text records were assessed for eligibility. Consultations and reference checking produced additional 13 full-text records for eligibility assessment. Of the 107 full-text records, 43 were finally included in this scoping review. Details of the search results and screening process are presented in Fig. 1.

Fig. 1
figure 1

PRISMA flow diagram of articles on ALRTIs among children under five in SSA

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Characteristics of included studies

The majority of the included studies were cross-sectional surveys (33) and case–control studies (6). See the details of the study designs of included studies in Fig. 2. Most of the included studies were conducted in Ethiopia (16), Nigeria (6) and Uganda (5). See the details of countries where included studies were conducted in Fig. 3. Included studies used a total sample size of 526,667. Furthermore, most of the reviewed studies were conducted on risk factors (41) and prevalence (28). See the details of reviewed studies based on the objectives of this scoping review in Fig. 4. Also, the details of extracted data are presented in Table 2.

Fig. 2
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Study designs of included studies on ALRTIs among children under five in SSA

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Fig. 3
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Countries included studies on ALRTIs among children under five in SSA

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Fig. 4
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Studies based on objectives of the review on ALRTIs among children under five in SSA

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Table 2 Data extraction for included studies
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Findings

Prevalence of ALRTIs in SSA

There is a high prevalence of ALRTIs among children under five in SSA. Thus, the prevalence rate of pneumonia includes 59.2% [46], 22.3% [15], 31.6% [14], 13.2% [18] and 9.0% [41]. Prevalence of Bronchiolitis reported in the studies were6.9% [14] and 1.9% [18]. Among reviewed studies, 60.2% [42] and 1.9% [18] were the highest and lowest reported prevalence of ALRTIs, respectively. Furthermore, seven studies reported a prevalence between 1 and 10% [14, 18, 22, 29, 30, 41, 44]. The majority of the reviewed studies that provided the rates were between 11 and 20% [18, 19, 28, 31-34, 47]. Additionally, seven studies reported a prevalence between 21 and 30% [7, 15-17, 23, 24, 35] and four studies recorded a prevalence between 31 and 40% [14, 36, 43, 49]. Only one study provided a prevalence between 41 and 50% [1]. Finally, three studies provided a prevalence between 51% and 57.5% and were among hospitalised samples [13, 46]. Compared to studies that used community samples, studies that used hospitalised samples reported relatively higher prevalence of ALRTIs. For instance, 6 studies that used hospitalised samples reported prevalence above 30% [1, 13, 14, 46, 49]. See details in Table 2.

Risk factors of ALRTIs of children under five in SSA

The reviewed studies showed that children above the age of 2 years are at higher risk of ALRTIs [7, 13, 16, 19, 25, 33, 37, 43, 47]. However, this evidence is inconclusive because children under 2 years seem highly susceptible to ALRTIs compared to the rest of children under five [13, 16, 25]. Moreover, children under five of teenage mothers [16, 22, 25] and children from mothers above age 35 [26] are more susceptible to ALRTIs. Evidence strongly establishes that children of mothers with low education [14, 15, 22, 29, 31-33, 36, 48, 50] and lack of employment [26, 30] are more vulnerable to developing ALRTIs. However, evidence on the risk of children’s residence for ALRTIs is inconsistent as some studies attributed it to rural dwellings [16, 23, 43, 48] while others attributed it to urban areas [13, 14, 31]. The review further shows that high-order births [43], large family sizes (above five) or crowded households [14, 18, 19, 22, 28, 53] and low household income [43, 48] are likely to predispose children under five to ALRTIs. Finally, children under five in households with poor hygienic practices, such as poor or irregular handwashing [16, 38] and cockroach infestation [20] are likely to be diagnosed with ALRTIs.

Poor ventilation or the absence of windows [1, 26, 35, 53], households without separate kitchens [18] electricity [31], clean water or improved toilet facilities [33] put children at risk of ALRTIs. Also, evidence shows that inhouse cooking [28, 32, 34, 47], usage of solid fuel [20, 22, 27, 53] or unclean fuel such as cow dung [14, 22, 26, 43] increase the risk of children to ALRTIs, especially those living in households with inadequate ventilation. Perhaps, children under 5 years who are held by their mothers while cooking [26, 35] and exposure to unclean and solid fuels for cooking [20, 22, 27, 53] may be at risk of developing various ALRTIs. Moreover, children under five exposed to cigarette smoke [14, 15, 35, 50] and wood smoke [15] may suffer more from ALRTIs complications.

Malnourished children under five are more likely to suffer ALRTIs complications [14, 26, 28, 43, 44, 48, 50]. For instance, children under five who are underweight [22, 33] or stunted [33, 37], and those anaemic [13] and not exclusively breastfed or poorly breastfed [1, 14, 22, 36] are more likely to suffer ALRTIs. Unfortunately, unvaccinated children under five [1] or children who did not complete their vaccination [46] or did not receive vitamin A supplements [13, 29, 30] are at higher risk of ALRTIs. Perhaps, children with existing health issues such as HIV [15] and a history of diarrhoea [19, 29-31, 33] become more vulnerable to ALRTIs (See Table 3 for details).

Table 3 Risk factors of ALRTIs among children under five in SSA
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Interventions to reduce ALRTIs among children under five in SSA

Some reviewed studies reported interventions that have been put in place to protect children under five against ALRTIs. Evidence shows that health promotion strategies such as campaigns and health education have doubled the health-seeking behaviours of mothers of children under 5 years of age against ALRTIs in Uganda [43]. However, a report from Niger indicates that multiple home visits for post-hospitalisation health monitoring were not more effective at preventing ALRTIs-related morbidity and mortality among under five children [46]. Similarly, evidence from Ethiopia shows that improvements made to baking stoves had appreciable effect on ALRTI among under five children [47]. Furthermore, evidence shows misuse of antibiotics, anti-malaria and herbal medicines to treat ALRTIs among these children [41, 42].

Discussions

Findings show a high prevalence (between 1.9% to 60.2%) of ALRTIs among children under five of age in Africa. Predictors of ALRTIs among under five children include poor education, poverty, malnutrition, exposure to second-hand smoke, poor ventilation, HIV, traditional cooking stoves, unclean fuel usage, poor sanitation facilities and unclean source of drinking water.

Prevalence of ALRTIs

The prevalence of ALRTIs among children under 5 years in SSA is relatively higher, with most studies reporting a prevalence between 10 and 60%. Perhaps, the use of demographic health surveys and hospitalised samples in most studies might result in the high prevalence rate of ALRTIs among children.. For instance, high prevalence rate of ALRTIs may be found among hospitalised samples because mostly such population may present symptoms to hospitals for treatments or diagnosis. Pneumonia consistently showed a high prevalence among children under five in SSA, regardless of the study design [14, 18, 46]. Higher prevalence of pneumonia in children might be one of the contributors of high numbers of deaths reported in SSA due to pneumonia [3, 10]. Studies that relied on self-reported symptoms are likely to report misleading prevalence because self-report symptoms may not produce a good diagnosis of ALRTIs among children.

Risk factors of ALRTIs among children under five in SSA

Evidence from reviewed studies shows that malnutrition affects children under five and is likely to expose these children to severe ALRTIs [26, 28]. Perhaps, ALRTIs are highly prevalent in SSA because of the increasing trend in malnutrition in SSA [54, 55]. Moreover, exclusive breastfeeding serves as a protective factor for children under five against ALRTIs [56]. Though almost all infants in SSA are breastfed, exclusive breastfeeding is less common [51]. This situation makes it difficult to protect children under five from ALRTIs because only 33% of infants are exclusively breastfed in SSA [51]. Unfortunately, the review found that children infected with HIV are highly vulnerable to ALRTIs [56, 57]. Thus, pneumonia, for instance, frequently occurs as an opportunistic infection in HIV-infected children, especially among children in a region highly burdened by HIV [45, 57].

Low maternal education and socioeconomic status and factors such as poor toilet and drinking water facilities are significantly associated with ALRTIs among children under five. The effect of socioeconomic and demographic determinants on morbidity and mortality among children is well-established [10]. However, factors such as the specific age of children under five, maternal age and residence settings as risk factors for ALRTIs among under five children in SSA have shown inconsistent results. These factors many need further research attention. Low socioeconomic status is likely to increase the ALRTIs risk for children under 5 years through several factors, such as poor nutritional status, poor housing conditions, overcrowding, the use of unclean fuel and reduced access to health care and preventive programmes [28].

Furthermore, children under five exposed to smoke through the use of hard and unclean fuels as well as second-hand tobacco smoke, are likely to suffer from ALRTIs. Although high-quality studies with robust designs are needed, this finding is relevant since almost 40% of the children globally, especially those in resource-poor settings like SSA, are exposed to second-hand tobacco smoke [10]. Furthermore, this finding is significant given the fact that most SSA countries are heavily reliant on unclean cooking fuels due to multifaceted socioeconomic difficulties.

Interventions to reduce ALRTIs among children under five in SSA

There is a lack of evidence regarding existing interventions in improving ALRTIs among children under five in SSA. For instance, evidence shows that health promotion activities such as multiple home visits by community health nurses p are not effective in preventing ALRTIs among children under 5 years [46]. Perhaps, this finding may be due to a lack of high-quality studies exploring the benefits of home visits in preventing ALRTIs. In addition, evidence shows that using an improved cooking stove does not serve as a protective factor against ALRTIs among children under five in SSA [47]. Thus, this demonstrates the lack of intervention studies to guide policies. This provides an opportunity for designing intervention research for preventing ALRTIs from children under five in SSA.

Policy recommendations

Education and socioeconomic development need to be included in the list of interventions to reduce ALRTI morbidities and mortalities among children under 5 years not only because it is their fundamental rights but also because multisectoral and interdisciplinary approaches that go beyond treatment are increasingly recognised as efficient ways to address global health inequalities and improving lives of our children. This review provides evidence to support the need for additional interventions with the greatest potential for reducing the burden of ALRTIs among under five children in SSA. There is a need for health systems in SSA to strengthen antenatal care, optimal maternal physical and mental health, and HIV control in HIV-infected mothers.

Additionally, good ventilation is to be encouraged in homes. Clean cooking fuels should be promoted through subsidised programmes and education. Policies should direct governments in SSA to invest in providing decent and affordable housing and sanitation facilities for its citizens. Primarily, quality housing should be provided to poor people and those in vulnerable situations, such as street mothers and displaced communities, to help protect their children from ALRTIs. In addition, intersectoral collaboration is essential to strengthen poverty alleviation strategies, improve living conditions, optimise child nutrition, ensure all children have access to clean running water, and reduce the burden of ALRTIs among under five children in SSA.

Recommendations for future studies

High-quality studies such as randomised controlled-trials and longitudinal studies that adjust for confounding variables are needed to explore how health promotion strategies like the use of improved cooking stoves and nutritional interventions protect against ALRTIs among children under five in SSA. Furthermore, there is a need for high-quality studies to explore factors such as specific age and place of residence (Rural or urban) of children under five that make them more susceptible to ALRTIs. Though there is some evidence that second-hand tobacco smoke and mothers’ age contribute to ALRTIs, existing studies are insufficient to confirm these findings in SSA. Hence, there is a need for more studies to explore these linkages. Finally, studies evaluating existing interventions on reducing ALRTIs among under five children in SSA are needed to determine which type of interventions are most effective at reducing ALRTIs among this young population.

Limitations

One major limitation of this review is its lack of accounting for confounders in most reviewed studies. Besides, studies that used self-report measures to estimate the prevalence of ALRTIs may impede the generalisation of findings. In addition, language limitations may prevent authors from retrieving studies published in other languages, which could have added more strength to this review. However, this review used a comprehensive search strategy to help map relevant evidence to inform policy, interventions and future research.

Conclusion

This scoping review aims to map evidence on prevalence, risk factors and interventions of ALRTIs among children under 5 years in SSA to inform future studies and help develop robust and effective policies and interventions in preventing and protecting children under 5 years. The findings show a high prevalence of ALRTIs, especially pneumonia, among children under five in SSA. Poor education of caregivers, poverty, malnutrition, exposure to second-hand tobacco smoke, poor ventilation, HIV, traditional cooking stoves and unclean fuel usage, poor sanitation facilities and unclean source of drinking water makes children under five more vulnerable to ALRTIs in SSA. Intersectoral collaboration are essential in SSA to reduce the burden ALRTIs among children under five. There is a need to strengthen poverty alleviation strategies, improve living conditions, optimise child nutrition, and ensure that all children have access to clean running water on the continent.