ArticlesGlobal burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis
Introduction
Acute lower respiratory infections (ALRI) such as pneumonia and bronchiolitis are a leading cause of morbidity and mortality in young children.1 Around 156 million new episodes of ALRI occur worldwide every year and about 1·56 million young children died as a result of such infections in 2008.2, 3 Respiratory viruses are commonly associated with ALRI episodes in young children.4, 5, 6, 7, 8, 9, 10 We previously estimated that respiratory syncytial virus (RSV) is present in 22% of such episodes, making it the most prevalent pathogen in children with ALRI.11 Influenza has long been regarded as an important disease in the elderly because of its high incidence and concomitant high rate of hospital admissions and mortality in individuals older than 65 years.12 However, studies in the past decade suggested that the burden of disease due to hospital admissions for influenza-associated ALRI in young and very young children is also substantial.13, 14, 15, 16
Previously, no estimates of the global burden of disease from seasonal influenza virus-associated ALRI in young children have been made. We identified only two systematic reviews of the incidence of influenza-associated pneumonia,17, 18 neither of which provided summary incidence rates. Recent estimates of global ALRI incidence and mortality associated with Streptococcus pneumoniae, Haemophilus influenzae type b, and RSV11, 19, 20 do not fully explain the paediatric ALRI burden, and so the role of other pathogens needs to be explored. Influenza is associated with a large but unknown number of hospital admissions in young children globally and is vaccine preventable. Globally, there is an increasing capacity for laboratory-confirmed diagnosis of influenza infection which led to increased recognition (especially) of severe influenza-related illness in children and adults in developing countries during the influenza A H1N1 pandemic in 2009. Additionally, studies from developing countries have provided population-based estimates of burden of influenza in children that have added to the evidence of the health effects of the disease worldwide. Moreover, the influenza A H1N1 (2009) pandemic raised questions about the baseline incidence and mortality from seasonal influenza in young children so as to better assess the need for and structure of vaccination programmes.
Many data for incidence and mortality from influenza-associated ALRI in developing countries remain unpublished. Therefore, we formed an international Influenza Study Group to supplement our systematic literature review with unpublished data. We aimed to estimate the burden of disease due to influenza-associated ALRI in children younger than 5 years for 2008 globally and for six WHO regions.
Section snippets
Search strategy and selection criteria
We undertook a systematic literature review with various search terms (webappendix pp 3–4) and hand searched online journals and scanned reference lists of identified citations. We restricted the search to Medline (Ovid), Embase, CINAHL, Global Health, Web of Science, WHOLIS, LILACS, IndMed, grey literature (SIGLE), and Chinese language databases and to studies published between Jan 1, 1995, and Oct 31, 2010. Panel 1 shows study eligibility criteria. No language or publication restrictions were
Results
We identified 43 studies15, 16, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54 with suitable data (table 1, figure 2): 18 were population-based studies reporting incidence of influenza-associated severe or non-severe ALRI in populations under surveillance; 10 were studies estimating incidence on the basis of hospital-discharge records or laboratory reports and a census-based denominator of children at risk; and 15 were population-based studies
Discussion
Our study is the first to estimate global incidence of influenza-associated ALRI and resultant mortality in children younger than 5 years. We estimated that, in 2008, there were about 90 million (95% CI 49–162 million) new cases of influenza episodes, 20 million (13–32 million) cases of influenza-associated ALRI, and 1 million (1–2 million) cases of influenza-associated severe ALRI in this group, causing 28 000–111 500 deaths. Estimates are very variable within countries or regions and between
References (89)
- et al.
Global, regional, and national causes of child mortality in 2008: a systematic analysis
Lancet
(2010) - et al.
Etiologic agents and outcome determinants of community-acquired pneumonia in urban children: a hospital-based study
J Natl Med Assoc
(2008) - et al.
Global burden of acute lower respiratory infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis
Lancet
(2010) - et al.
Burden of disease caused by Streptococcus pneumoniae in children younger than 5 years: global estimates
Lancet
(2009) - et al.
Burden of disease caused by Haemophilus influenzae type b in children younger than 5 years: global estimates
Lancet
(2009) - et al.
Meta-analysis in clinical trials
Control Clin Trials
(1986) - et al.
Rates of hospitalisation for influenza, respiratory syncytial virus and human metapneumovirus among infants and young children
Vaccine
(2006) - et al.
Influenza-related hospitalisations among children aged less than 5 years old in the Basque Country, Spain: a 3-year study (July 2001–June 2004)
Vaccine
(2005) - et al.
Burden of seasonal influenza hospitalization in children, United States, 2003 to 2008
J Pediatr
(2010) - et al.
Clinical features of Malaysian children hospitalized with community-acquired seasonal influenza
Int J Infect Dis
(2010)
Health-seeking patterns among participants of population-based morbidity surveillance in rural western Kenya: implications for calculating disease rates
Int J Infect Dis
The global burden of disease: 2004 update
Epidemiology and etiology of childhood pneumonia
Bull World Health Organ
Viral respiratory infections and their role as public health problem in tropical countries (review)
Afr J Med Med Sci
The epidemiology of acute respiratory infections in children and adults: a global perspective
Epidemiol Rev
Role of respiratory viruses in acute upper and lower respiratory tract illness in the first year of life: a birth cohort study
Pediatr Infect Dis J
Respiratory viruses in the pediatric intensive care unit: prevalence and clinical aspects
Mem Inst Oswaldo Cruz
Etiology and epidemiology of viral pneumonia among hospitalized children in rural Mozambique: a malaria endemic area with high prevalence of human immunodeficiency virus
Pediatr Infect Dis J
Viral etiology of severe pneumonia among Kenyan infants and children
JAMA
The burden of influenza in children
Curr Opin Infect Dis
Influenza-associated hospitalizations in the United States
JAMA
Vaccine preventable diseases and vaccination coverage in Australia 2001 to 2002
Commun Dis Intell
Burden of interpandemic influenza in children younger than 5 years: a 25-year prospective study
J Infect Dis
The underrecognized burden of influenza in young children
N Engl J Med
Incidence of influenza and associated illness in children aged 0–19 years: a systematic review
Rev Med Virol
The burden of influenza in East and South-East Asia: a review of the English language literature
Influenza Other Respir Viruses
Case management of acute respiratory infections in children in developing countries. Report of a working group
Strategy to enhance influenza surveillance worldwide
Emerg Infect Dis
Influenza and the rates of hospitalization for respiratory disease among infants and young children
N Engl J Med
The Global Burden of Diseases, Injuries and Risk Factors Study. Operations Manual Final Draft
The State of the World's Children Special Edition
Global estimate of the incidence of clinical pneumonia among children under five years of age
Bull World Health Organ
Use of verbal autopsy by health workers in under-five children
Indian Pediatr
Seasonal pattern of pneumonia mortality among under-five children in Nairobi's informal settlements
Am J Trop Med Hyg
Burden of influenza in children in the community
J Infect Dis
Viral pathogens associated with acute respiratory infections in central Vietnamese children
Pediatr Infect Dis J
Assessing disease burden of respiratory disorders in Hong Kong children with hospital discharge data and linked laboratory data
Hong Kong Med J
Virologically confirmed population-based burden of hospitalization caused by influenza A and B among children in Hong Kong
Clin Infect Dis
The epidemiology of hospitalized influenza in children, a two year population-based study in the People's Republic of China
BMC Health Serv Res
Population-based surveillance for hospitalizations associated with respiratory syncytial virus, influenza virus, and parainfluenza viruses among young children
Pediatrics
Epidemiology, complications, and cost of hospitalization in children with laboratory-confirmed influenza infection
Pediatrics
Multistate surveillance for laboratory-confirmed, influenza-associated hospitalizations in children: 2003–2004
Pediatr Infect Dis J
Influenza is a major contributor to childhood pneumonia in a tropical developing country
Pediatr Infect Dis J
The descriptive epidemiology of severe lower respiratory tract infections in children in Kiel, Germany
Klin Padiatr
Cited by (729)
Human Bocavirus infection in childhood acute respiratory infection: Is it an innocent bystander?
2023, Indian Journal of Medical Microbiology
- ‡
Joint corresponding authors