- Open Access
Viral pneumonia in adults and older children in sub-Saharan Africa — epidemiology, aetiology, diagnosis and management
© The Author(s) 2014
- Received: 26 February 2014
- Accepted: 27 June 2014
- Published: 1 December 2014
Community-acquired pneumonia causes substantial morbidity and mortality in sub-Saharan Africa with an estimated 131 million new cases each year. Viruses — such as influenza virus, respiratory syncytial virus and parainfluenza virus — are now recognised as important causes of respiratory disease in older children and adults in the developed world following the emergence of sensitive molecular diagnostic tests, recent severe viral epidemics, and the discovery of novel viruses. Few studies have comprehensively evaluated the viral aetiology of adult pneumonia in Africa, but it is likely to differ from Western settings due to varying seasonality and the high proportion of patients with immunosuppression and co-morbidities. Emerging data suggest a high prevalence of viral pathogens, as well as multiple viral and viral/bacterial infections in African adults with pneumonia. However, the interpretation of positive results from highly sensitive polymerase chain reaction tests can be challenging. Therapeutic and preventative options against viral respiratory infections are currently limited in the African setting. This review summarises the current state of the epidemiology, aetiology, diagnosis and management of viral pneumonia in sub-Saharan Africa.
- viral pneumonia
- viral respiratory tract infections
- older children
- sub-Saharan Africa
Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality in all age groups worldwide (1). The African continent carries a substantial burden — around 30% of the estimated 430 million episodes of lower respiratory tract infections (LRTI) each year (1). Bacteria, for example, Streptococcus pneumoniae, are the principal causative agents in adult pneumonia (2, 3). However, the availability of sensitive molecular tests has resulted in the increasing recognition of viruses as major contributors (4, 5). Moreover, the emergence of avian influenza A(H5N1) virus and 2009 pandemic influenza A(H1N1) virus, along with the accelerated discovery of other novel respiratory viruses (e.g., human metapneumovirus [hMPV], bocavirus, coronaviruses NL63 and HKU1, Middle East Respiratory Syndrome [MERS]), against a backdrop of a growing population of immunocompromised individuals has catalysed research attention on severe viral respiratory infections in adults.
Available data on the contribution of viruses to adult CAP comes mainly from studies in developed settings (4, 5). Viral causes of pneumonia in African adults are less well characterised, largely due to the lack of access to appropriate diagnostics. The epidemiology, aetiological agents, seasonality, and age distribution of patients are likely to differ substantially from the developed setting for a myriad of reasons. Firstly, respiratory viruses typically follow seasonal patterns. In contrast to the distinct winter epidemics as seen in temperate regions, available influenza data indicate year round transmission in most African regions (6). Secondly, high prevalence of human immunodeficiency virus (HIV) infection and other comorbidities (e.g., tuberculosis [TB]) are likely to impact on the epidemiology and microbial aetiology of adult viral respiratory presentations (7). Several pneumonia aetiology studies in Africa have described a preponderance of younger adults (aged 15–45 years) (8, 9). Additionally, LRTI with herpes viruses, such as cytomegalovirus (CMV), herpes simplex virus (HSV) and varicella zoster virus (VZV), are common in adults in Western settings (10) and children in sub-Saharan Africa (11) with advanced immunosuppression. Moreover, immunocompromised patients may have more severe presentations. Emerging data from South Africa describes higher risk of death in HIV-infected adults with influenza infection (12). Lastly, many developed settings recommend targeted (13) or universal (14) seasonal influenza vaccination, but few African countries have national influenza vaccination programmes (15).
This paper reviews the current knowledge on the epidemiology and aetiology of viral pneumonia in adults and older children in sub-Saharan Africa, and evaluates the available options for diagnosis, prevention and management, and viral respiratory pathogens in this resource-poor setting.
The absence of a standardised case definition has been a longstanding problem of pneumonia aetiology studies. Most studies undertaken in developed settings have focused on radiologically-confirmed pneumonia (i.e. the presence of new infiltrates on chest radiograph [x-ray] with clinical symptoms suggestive of LRTI) (16–25). Given the inconsistent availability of chest radiographs in African health settings (26), a broader definition of pneumonia was used to include clinical evidence of LRTI with or without confirmed chest radiograph changes.
A literature search of original research articles using the PubMed database from inception through 31 May 2014 was conducted. The following PubMed search strategy was used: (“acute respiratory infection”[All Fields] OR “acute lower respiratory tract infection” [All Fields] OR “severe acute respiratory infection”[All Fields] OR “pneumonia”[All Fields] OR “pneumonia”[ MeSH Terms]) AND (“Africa” [MeSH Terms] OR “Africa” [All fields]).
Characteristics of studies on viral aetiology in hospitalised adults and older children with pneumonia or clinical lower respiratory tract infection in sub-Saharan Africa.
Study, year [ ] Reference
Viral diagnostic test
Joosting et al., 1979 
May 1966–Apr 1972
Hospital-based observational study
Acute respiratory disease (definition not stated)
Throat swabs & serum
Viral culture & serology (HAI or complement fixation)
Scott et al., 2000 
Mar 1994–May 1996
Hospital-based observational study
Pneumonia (>2 symptoms of fever, cough, sputum, chest pain, SOB, or haemoptysis; symptoms <14 days; consolidation on CXR)
Hartung et al., 2011 
Feb 2006–Sept 2006
Hospital-based observational study
Pneumonia (>1 symptom of cough, sputum, chest pain, SOB, chest pain or haemoptysis; CXR changes) + admission to HDU
Feikin et al., 2012 
Mar 2007–Feb 2010
ARI (cough or difficulty breathing or chest pain and temperature >38.0 °C or oxygen saturation <90% or hospitalisation)
NP & OP swabs
Pretorius et al., 2012 
Feb 2009–Dec 2010
Hospital-based surveillance (6 hospitals)
SARI (fever; cough or sore throat; shortness of breath or difficulty breathing; symptoms <7 days)
NP & OP swabs
Results of studies on viral aetiology in hospitalised adults and older children with acute lower respiratory tract infection or pneumonia in sub-Saharan Africa
Study, year [ ] Reference
Joosting et al., 1979a 
Any: 384 (37.9%)
A: 287 (28.4%)
B: 87 (8.6%)
Scott et al., 2000b 
A: 12 (4.3%)
B: 2 (0.7%)
Hartung et al., 2011c 
PIV1: 1 (9%)
Bocavirus: 1 (9%)
Coronavirus NL63: 1 (9%);
Coronavirus OC43: 1 (9%)
Feikin et al., 2012e 
Any: 37 (9%)
A: 29 (7%)
B: 8 (2%)
PIV1: 2 (0.5%)
PIV2: 6 (2.0%)
Pretorius et al., 2012i 
5–24 years: 51%
25–44 years: 33.8%
45–64 years: 28.7%
>65 years: 24.2%
Any: 343 (8.6%)
A(H3N2): 102 (2.5%)
A(H1N1): 104 (2.6%)
B: 137 (3.4%)
Any: 145 (3.4%)
PIV1: 12 (0.3%)
PIV2: 27 (0.7%)
PIV3: 96 (2.4%)
Enterovirus: 63 (1.6%)
The percentage of patients with at least one viral pathogen ranged from 5.7% to 58% (Table 2), which is comparable to the 11–56% reported in contemporary studies in developed settings (16–21, 47). The earliest study, conducted in South African black miners hospitalised with acute respiratory disease (definition not stated), reported detection of a respiratory virus in 47% of cases using viral culture and serology (44). In particular, a very high proportion of influenza A (28%) virus was found, even though whole years of observations were included. The authors attributed the prolonged influenza epidemic in the miners to the close working conditions that facilitated transmission and high staff turnover which maintained a large pool of susceptible individuals. In contrast, a prospective hospital-based study by Scott et al. (8) only identified a viral pathogen in 5.7% of adults with hospitalised pneumonia in Kenya. However, serology was the sole viral diagnostic method used to test for a small number of viruses.
A prospective observational study in pneumonia patients admitted to a high dependency unit (HDU) of a tertiary referral hospital in Malawi found a viral pathogen in 11 of 51 (22%) patients (45) — 3 had a final diagnosis of viral pneumonitis, whereas the rest had an alternative diagnosis (pulmonary Kaposi’s sarcoma) or pathogen (e.g., Mycobacterium tuberculosis) that was considered the primary cause for severe respiratory presentation. The study was limited to those who could tolerate a bronchoscopy (with resultant exclusion of 39% of eligible patients), which likely introduced selection bias. Moreover, two-thirds of patients had symptom duration of greater than 3 weeks, which may have accounted for the high proportion of Pneumocystis jiroveci pneumonia (PCP) (27%) and M. tuberculosis (22%).
The latest studies are derived from epidemiological surveillance in Kenya (39) and South Africa (41). Both studies reported high rates of viral infection — in particular, high prevalence of rhinovirus, enterovirus, influenza virus and adenovirus were found (Table 2). Feikin et al. (39) also enrolled asymptomatic hospital controls, hence the authors were able to infer the absence of association with clinical illness in a number of commonly identified viruses (namely, rhinovirus, enterovirus and adenovirus). Conversely, influenza A virus and RSV were significantly associated with hospitalised ARI. Pretorius et al. (41), the largest study to date with greater than 4,000 patients, was able to report age-stratified prevalence of detected viruses. They demonstrated the highest prevalence of viruses in hospitalised severe acute respiratory infection (SARI) patients aged 5–24 years (51%), compared to older age groups (25–44 years, 34%; 45–64 years, 29%; >65 years, 24%).
Outcome data were sparse among the included studies — mortality of 10% and 22% were reported by Scott et al. (8) and Hartung et al. (45), respectively; Feikin et al. (39) found a case fatality ratio of 6% in persons aged 5 years and over with hospitalised ARI. However, none of the studies reported clinical outcome according to underlying viral or bacterial aetiology. Moreover, there were limited data on high-risk groups such as HIV-infected individuals, adults with underlying co-morbidities, and the elderly. Feikin et al. (39) described higher incidence rates of all pathogens in HIV-infected compared to HIV-uninfected adults, but this analysis included both inpatients and outpatients. Pretorius et al. (41) did not find higher prevalence of virus in adults aged 65 years and over compared to younger age groups. Although beyond the scope of this review, young children are also an important risk group. The aetiology and risk factors for hospitalised pneumonia in this group are being addressed by the Pneumonia Etiology Research for Child Health (PERCH) project, a multi-site case control study in 7 countries, 5 of which are in sub-Saharan Africa (48).
3.1 Multiple pathogen infection
As a result of an expanding armamentarium of diagnostic tests, viral-viral and viral-bacterial co-infections are increasingly identified. Several studies in well-resourced settings have found more severe disease and poorer outcomes in patients with polymicrobial infections (16, 17, 19, 22). However, the clinical interpretation of mixed infections is not straightforward since detection of multiple pathogens could reflect three possible scenarios: i) all detected organisms have contributed to pathogenesis; ii) >1 detected organism is an innocent bystander; iii) one organism is the predisposing factor (e.g., by damaging the respiratory epithelium) to cause pneumonia by the second organism.
Influenza virus and S. pneumoniae is the most studied co-infection combination; their synergistic interaction is well described (49, 50). In the African setting, the pneumococcal conjugate vaccine (PCV) has been shown to prevent 31% of viral pneumonia in South African children (51), providing epidemiological evidence of the importance of pneumococcal co-infection in viral pneumonia. More recently, a hospital-based surveillance study in South Africa described elevated blood pneumococcal load (as a marker for invasive pneumococcal pneumonia) in patients with influenza virus co-infection (52).
All but one of the included African studies described mixed infection. Scott et al. (8) reported bacterial pneumonia in 8 of 12 cases with influenza. Viral co-infections (rhinovirus [n = 3]; coronaviruses OC43 and NL63; RSV and PIV type 1 [PIV1]) with bacteria/fungus (including Staphylocccus aureus, Klebsiella pneumoniae, P. jiroveci and M. tuberculosis) were demonstrated in 7 of 51 (14%) cases of the Malawian HDU cohort (45). The recent ARI surveillance study in Kenya demonstrated mixed viral and bacterial infections in 29% of patients (39, 41). Co-infections were more common in HIV-positive than HIV-negative patients, and influenza virus was less likely to be co-infected with other viruses, compared with other viral pathogens (39). Pretorius et al. (41) reported viral co-infections in 17% of hospitalised pneumonia patients (this included children <5 years), but were unable to correlate co-infection with clinical outcome due to the low number of specific co-infection combinations. Among co-infected patients in the Kenyan and South African studies, adenovirus, rhinovirus and RSV were the most frequently detected viruses. Feikin et al. (39) found a similar prevalence of rhinovirus and adenovirus in cases and controls, implying that their identification in ARI cases may not be clinically significant. Nonetheless, the contribution of these commonly identified viruses to disease severity is often unclear from available literature.
The role of rhinovirus in pneumonia is contentious. On one hand, asymptomatic carriage is well described in immunocompetent (53) and immunocompromised patients (54). Conversely, viral shedding beyond 2 weeks of acute illness is rare, suggesting an association with clinical disease (55, 56). Furthermore, rhinovirus has been associated with hospitalised LRTI in Thai adults (57), and has also been the suspected causative organism in several outbreaks of severe respiratory diseases in nursing homes in the United States (58, 59).
In contrast, asymptomatic carriage of adenovirus (60) and RSV (61) are uncommon. Hence their presence is usually pathogenic. Adenovirus has been implicated as a cause of pneumonia in South African and Chinese adults, although neither study had a control group (44, 62).
3.2 Limitations of current studies
Given the wide variation in time period, study population, pneumonia definition, clinical specimens, diagnostic methods, and number of pathogens tested, it is difficult to make any firm conclusions from the handful of studies available beyond that viral pathogens are prevalent in older children and adults in sub-Saharan Africa presenting with severe ARI. Mixed infections are common. With the exception of Feikin et al. , the lack of control group is a major limitation, as the background prevalence of asymptomatic viral infections is undefined (see section 4.2 for the role of healthy controls).
Antivirals against respiratory viruses are prohibitively expensive and largely unavailable in sub-Saharan Africa. Despite the likely prevalence of CMV pneumonitis, there are no published reports on ganciclovir use in adult CMV disease on the continent (11). With the exception of aciclovir for the treatment of HSV and VZV (74), anti-influenza agents, namely neuraminidase inhibitors (NI) (oseltamivir and zanamavir) and M2 inhibitors (amantadine and rimantadine), are the only antivirals available in a small number of African settings (15). Moreover, due to widespread resistance against seasonal influenza A(H3N2) virus and pandemic influenza A(H1N1) virus in recent years (75), M2 inhibitors are no longer recommended for the treatment or prophylaxis of influenza A virus (76).
NIs have been shown to be 68–92% effective in preventing influenza in healthy adults and children in developed settings (77). In a recent Cochrane review, oseltamivir was associated with a shortening of illness duration by 0.7 days (78). Due to the lack of diagnostic definitions, it is unclear whether NIs reduce the risk of influenza complications such as pneumonia (78), though they had no effect on rates of hospitalisation (78). Data on the impact of NIs on hospitalised or immunosuppressed patients with influenza pneumonia are scarce. Current evidence, largely derived from retrospective studies, suggests that oseltamivir accelerates viral clearance (79), reduces length of hospital stay (80) as well as lowers mortality in patients hospitalised with influenza (81, 82). Specifically in HIV-infected individuals, several studies have suggested that oseltamivir reduces severity of illness (83), but no prospective evaluation of the efficacy of NIs in HIV-infected individuals or in African settings has been undertaken.
NIs are most effective if administered within 48 hours of symptom onset (84). The lack of viral testing in ‘realtime’, broad differential diagnosis of acute respiratory presentations in high HIV prevalence settings, in addition to high cost and lack of availability, are barriers to the widespread and effective use of NIs in the region at present.
With a shortage of therapeutic options, prevention and control of viral pneumonia should be focused on infection control and vaccines. Core infection control measures, such as cohorting and isolation, are impractical in many resource-poor settings. However, physical interventions such as handwashing, use of masks, gloves and aprons may be feasibly implemented to minimise risk of nosocomial spread (85, 86).
Vaccine options are limited for the prevention of respiratory viral infections — the only approved vaccine is against seasonal influenza. In well-resourced settings, annual influenza vaccination with trivalent or quadrivalent inactivated vaccines (TIV/QIV) or an intranasal live attenuated vaccine (LAV) has an established role in preventing influenza infection and its complications (13, 14). LAV is contraindicated in immunosuppressed or pregnant patients, thus unsuitable for widespread use in sub-Saharan Africa where HIV prevalence is high. Only 2 studies have evaluated efficacy or effectiveness of TIV in Africa, both from South Africa. Age-adjusted vaccine effectiveness of TIV, estimated from a surveillance programme on patients with influenza-like illness (ILI), ranged from −14% (95% CI-100% to 35%) to 67% (95% CI 12%–90%) between 2005 and 2009, though low vaccine coverage (approximately 4% among ILI cases) may have reduced the power to estimate vaccine effectiveness (87). A randomised double blind placebo-controlled trial of TIV in HIV-infected adults demonstrated vaccine efficacy of 75.5% (95% CI 9.2%–95.6%) (88), which is comparable to that in developed settings (89). However, excluded patients with underlying co-morbidities and advanced immunosuppression (antiretroviral therapy naïve with CD4 <100 cells/µL). Evaluation of TIV or QIV efficacy in this high-risk group is required.
A recent CDC survey reported availability of seasonal influenza vaccine in 14 of 31 (45%) African countries (15). However, only 2 sub-Saharan African countries (Côte d’Ivoire and Mauritius) reported to have a national public policy for influenza vaccination. Even if annual seasonal influenza vaccination became national policy, its implementation will be logistically challenging. There is currently no indigenous vaccine production in the region (72). Additionally, the vaccine donation initiative that provided 2009 pandemic influenza (H1N1) virus vaccines also highlighted problems in vaccine procurement, distribution and uptake in the region (72).
A number of vaccines against other important viral pathogens such as RSV (90) and PIV type 3 (PIV3) (91) are under development. Furthermore, given the protective effect of pneumococcal vaccination on viral pneumonia in children (51), the current PCV roll-out in children in a number of African countries may result in an indirect benefit on adult viral pneumonia (92).
Increasing deployment of sensitive molecular diagnostic assays has improved our ability to characterise the contribution of viruses to adult pneumonia. Viruses commonly identified in CAP in the Western setting-namely rhinovirus, influenza virus, RSV and PIV — are prevalent in adults and older children presenting with hospitalised pneumonia in sub-Saharan Africa. Novel viruses such as hMPV and human bocavirus are increasingly identified. This review highlights the scarcity of literature on viral aetiology in adult CAP, especially in at-risk groups such as HIV-infected individuals, though data are beginning to emerge from SARI surveillance and prospective observational studies.
Vaccine and treatment options for viral respiratory pathogens remain limited and out of reach for most of sub-Saharan Africa, and evidence for their use in this setting is lacking. Nonetheless, ongoing epidemiological surveillance is important to evaluate temporal variations of circulating viruses and anticipate future outbreaks and pandemics. Better characterisation of the burden and spectrum of viruses that contribute to adult CAP in the region will also enable more informed interpretation of positive molecular results, aid decisions on important pathogens to include in respiratory disease surveillance programmes, as well as the most pathogenic viruses to target for vaccine and antiviral development. Furthermore, establishing a substantial burden of virus-associated severe respiratory infection (in particular influenza) may persuade local policy makers to consider targeted immunisation programmes — annual influenza vaccination in at-risk adults and PCV in children could potentially prevent a substantial proportion of viral pneumonia in adults.
Funding: This work was supported by the Wellcome Trust [Grant 097464]. The funder had no role in study design, collection and analysis of data, decision to publish, or writing of the manuscript.
Competing interests: AH declares no competing interests.
Provenance and peer review: Commissioned; no funding has been requested or received by the author for the preparation of the manuscript; externally peer reviewed.
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Copyright: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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