The global burden of lower respiratory infections: making progress, but we need to do better
Authors: David R Murdoch, Stephen R C Howie
Journal: The Lancet Infectious Diseases (2018)

Pneumonia is a major global killer of both children and adults. Much of its burden is preventable, which places an onus on the global health community to better direct efforts to reduce this burden. In response, WHO's Integrated Global Action Plan for the Prevention and Control of Pneumonia and Diarrhoea has set targets and a framework for tackling this challenge, an important component being to measure progress.1WHOUNICEFEnding preventable child deaths from pneumonia and diarrhoea by 2025: The integrated Global Action Plan for Pneumonia and Diarrhoea (GAPPD). World Health Organization, Geneva2013Google Scholar In The Lancet Infectious Diseases, the Global Burden of Disease (GBD) 2016 Lower Respiratory Infections Collaborators provide further estimates of the morbidity and mortality from lower respiratory infections, principally pneumonia and bronchiolitis.2GBD 2016 Lower Respiratory Infections CollaboratorsEstimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.Lancet Infect Dis. 2018; (published online Sept 19.)http://dx.doi.org/10.1016/S1473-3099(18)30310-4Google Scholar They also provide estimates for lower respiratory infections caused by four microorganisms—Streptococcus pneumoniae, Haemophilus influenzae type b, influenza, and respiratory syncytial virus. Published 1 year after their previous estimates,3GBD 2015 LRI CollaboratorsEstimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory tract infections in 195 countries: a systematic analysis for the Global Burden of Disease Study 2015.Lancet Infect Dis. 2017; 17: 1133-1161Summary Full Text Full Text PDF PubMed Scopus (411) Google Scholar the authors have included several new covariates as risk factors for lower respiratory infection, and report lower respiratory infection burden attributable to these risk factors. Similar to their previous findings, lower respiratory infections were a leading global infectious cause of mortality in all age groups (2 377 697 deaths, 95% UI 2 145 584–2 512 809), including in children younger than 5 years (652 572 deaths, 586 475–720 612) and among adults older than 70 years (1 080 958 deaths, 943 749–1 170 638).2GBD 2016 Lower Respiratory Infections CollaboratorsEstimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.Lancet Infect Dis. 2018; (published online Sept 19.)http://dx.doi.org/10.1016/S1473-3099(18)30310-4Google Scholar The findings indicate progress in the reduction of lower respiratory infection burden, although it varies across geographical regions, highlighting the need to maintain pneumonia prevention as a high priority activity. According to the models presented, S pneumoniae was the leading cause of lower respiratory infection morbidity and mortality globally, contributing to more than 1 million deaths, more than the other three aetiologies combined. Malnutrition was identified as a leading risk factor for lower respiratory infection mortality among children younger than 5 years and, together with air pollution (both household and ambient) and increased antibiotic use, was identified as a focus for targeted intervention measures. These summary points are relatively uncontentious. But it would be foolish to deny that there are methodological challenges, some contentious, in this field. If there were robust worldwide patient-level data for lower respiratory infection cases and deaths, there would be no controversy. This is not the case, and we rely on massaging the information available to produce global estimates. The problems with this approach are greatest where data are most scarce, the very places with the greatest burden—low-income and middle-income countries. It is not surprising, then, that different methods and estimates have emerged as groups grapple with issues such as quality versus quantity of data, and how best to handle those data to achieve useful approximations of the truth.4Kovacs SD Mullholland K Bosch J et al.Deconstructing the differences: a comparison of GBD 2010 and CHERG's approach to estimating the mortality burden of diarrhea, pneumonia, and their etiologies.BMC Infect Dis. 2015; 15: 16Crossref PubMed Scopus (38) Google Scholar The GBD Study group of the Institute for Health Metrics and Evaluation, who did this study, and WHO's Maternal and Child Epidemiology Estimation (MCEE) group are major players in the estimation of global childhood lower respiratory infection mortality, and their estimates for children younger than 5 years differ substantially (700 554 vs 920 000 deaths respectively),5Liu L Oza S Hogan D et al.Global, regional, and national causes of under-5 mortality in 2000-2015: an updated systematic analysis with implications for the Sustainable Development Goals.Lancet. 2016; 388: 3027-3035Summary Full Text Full Text PDF PubMed Scopus (1723) Google Scholar as do other pathogen-specific estimates.6Wahl B O'Brien KL Greenbaum A et al.Burden of Streptococcus pneumoniae and Haemophilus influenzae type b disease in children in the era of conjugate vaccines: global, regional, and national estimates for 2000–15.Lancet Global Health. 2018; 6: e744-e757Summary Full Text Full Text PDF PubMed Scopus (480) Google Scholar Additionally, mistrust of estimates has historically been fuelled by a perceived lack of transparency (so called black-box methods) and their shifting nature (“readily adaptable to changes in methodology”, the GBD team assure us). Nevertheless, the authors deserve credit for increasing transparency and also deserve our understanding as they generate their best estimates. But we must look at the data with eyes fully open to their limitations. What can we say with certainty? The burden of lower respiratory infection is huge, progress is being made, but we must do better. The GBD 2016 update highlights the burden of pneumonia in both children and adults. Efforts to reduce lower respiratory infection deaths must remain a top priority. The global health community might debate the relative priority to be given to key risk factors and interventions, but there will be broad support for the call to better tackle malnutrition and air pollution and to optimise case management, including the use of antibiotics, which emerge as priorities from the study. The effect of the pneumococcal conjugate vaccine in children is substantial,7Cohen R Cohen JF Chalumeau M Levy C Impact of pneumococcal conjugate vaccines for children in high- and non–high-income countries.Expert Rev Vaccines. 2017; 16: 625-640Crossref PubMed Scopus (47) Google Scholar, 8WHOPneumococcal vaccines WHO position paper—2012.Wkly Epidemiol Rec. 2012; 87: 129-144PubMed Google Scholar and further clarity concerning the likely role of pneumococcal vaccination in protecting adults is needed. Rapid progress is being made in the development of vaccines and monoclonal antibodies against respiratory syncytial virus,9Karron RA Zar HJ Determining the outcomes of interventions to prevent respiratory syncytial virus disease in children: what to measure?.Lancet Respir Med. 2018; 6: 65-74Summary Full Text Full Text PDF PubMed Scopus (19) Google Scholar and the importance of influenza vaccines must not be forgotten. Interventions to enhance access to health care are needed to augment preventive measures. Moreover, a greater understanding is needed of the role of individual respiratory pathogens (more than just the four included in this study), to provide more accurate estimates of disease burden and to better target interventions. Studies such as Pneumonia Etiology Research for Child Health Study10Levine OS O'Brien KL Deloria-Knoll M et al.The Pneumonia Etiology Research for Child Health Project: a 21st century childhood pneumonia etiology study.Clin Infect Dis. 2012; 54: S93-S101Crossref PubMed Scopus (141) Google Scholar will help in this respect. Lower respiratory infection remains a challenge to the global health community and one that must be tackled head on. DRM declares no competing interests. SRCH has a patent pending for lipocalin-2 as a biomarker of pneumococcal infection status. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016Our findings show substantial progress in the reduction of lower respiratory infection burden, but this progress has not been equal across locations, has been driven by decreases in several primary risk factors, and might require more effort among elderly adults. By highlighting regions and populations with the highest burden, and the risk factors that could have the greatest effect, funders, policy makers, and programme implementers can more effectively reduce lower respiratory infections among the world's most susceptible populations. Full-Text PDF Open Access