Conceived and designed the experiments: NH SPL WAP CBS Mahmudur Rahman ASMA ESG RZ AF M-AW RH EA-B JB Mustafizur Rahman. Performed the experiments: NH RV FZ MA EA-B. Analyzed the data: NH RV KH Mustafizur Rahman TA DDE EA-B. Contributed reagents/materials/analysis tools: RH DDE ESG. Wrote the paper: NH.
The authors have declared that no competing interests exist.
Pneumonia is the leading cause of childhood death in Bangladesh. We conducted a longitudinal study to estimate the incidence of virus-associated pneumonia in children aged <2 years in a low-income urban community in Dhaka, Bangladesh.
We followed a cohort of children for two years. We collected nasal washes when children presented with respiratory symptoms. Study physicians diagnosed children with cough and age-specific tachypnea and positive lung findings as pneumonia case-patients. We tested respiratory samples for respiratory syncytial virus (RSV), rhinoviruses, human metapneumovirus (HMPV), influenza viruses, human parainfluenza viruses (HPIV 1, 2, 3), and adenoviruses using real-time reverse transcription polymerase chain reaction assays.
Between April 2009–March 2011, we followed 515 children for 730 child-years. We identified a total of 378 pneumonia episodes, 77% of the episodes were associated with a respiratory viral pathogen. The overall incidence of pneumonia associated with a respiratory virus infection was 40/100 child-years. The annual incidence of pneumonia/100 child-years associated with a specific respiratory virus in children aged <2years was 12.5 for RSV, 6 for rhinoviruses, 6 for HMPV, 4 for influenza viruses, 3 for HPIV and 2 for adenoviruses.
Young children in Dhaka are at high risk of childhood pneumonia and the majority of these episodes are associated with viral pathogens. Developing effective low-cost strategies for prevention are a high priority.
Pneumonia is one of the major causes of childhood death causing annually 2 million deaths worldwide
According to WHO estimates Bangladesh is one of the 10 countries where two thirds of the pneumonia death are concentrated
We obtained written informed consent from the mother, father and an adult primary caregiver for all children enrolled in the study. The Institutional Review Board at International Centre for Diarrhoeal Disease Research, Bangladesh, (icddr,b) approved the study and the Institutional Review Board at Centers for Disease Control and Prevention (CDC), USA deferred to icddrb's approval.
We conducted our study in ward three of Pallabi thana (“thana” is the lowest administrative unit in Bangladesh). This ward of low-income community is in the north-west part of Dhaka and covers an area of 3.4 sq. km. The estimated population of the ward is 69,960; half of its population is male. The mean literacy rate is 69% for males and 59% for females
In January 2008, icddr,b initiated surveillance among a cohort of children in the study area to assess immunity to human amebiasis. All children who were born in the study area and lived within 1.5 kms of the study clinic, were enrolled at birth and followed prospectively. Our study was conducted on this existing birth cohort of children. In April 2009, when we started our longitudinal respiratory disease study we re-enrolled all children who were already participating in the amebiasis birth cohort and were aged 0–2 years. Subsequently we treated the population as an open cohort because we continued to enroll all children who were born in the study area after the April 2009 enrollment. We subsequently followed the cohort of children including children who were enrolled in the beginning of the study in April 2009 and children who were born after beginning of the study until March 2011. Children who were already part of the ongoing amebiasis birth cohort were not under any interventional study.
As part of on the ongoing amebiasis study, field assistants measured height and weight of each of the enrolled child within three days of birth. When we re-enrolled children into our study which began in April 2009, field workers trained in collecting surveillance data using hand held devices collected additional information from each child, including level of parental education and breast feeding practices. Prospectively, field workers visited each child at home twice weekly for two years of the study, to identify whether the child developed any major symptoms of respiratory illness, including subjective fever; rapid, laboured or noisy breathing; lethargy; cyanosis; inability to drink; or convulsion or minor symptomsincluding cough, rhinorrhoea, sore throat, muscle or joint pain, chills, headache, irritability, decreased activity and repeated vomiting within the last 72 hours of follow-up
In the clinic, study physicians collected a history of illness including signs and symptoms using a structured questionnaire, conducted a physical examination, and collected nasopharyngeal wash from each child every time a child presented with a new episode of reported or documented fever (T≥38°C) or respiratory symptoms including cough, nasal discharge or difficulty in breathing. An episode was considered to be new if the child had been symptom free in the preceding 7 days.
The study physician diagnosed a child with acute respiratory tract infection (ARI) if the child had cough and/or runny nose and diagnosed a child with pneumonia, if the child had cough or difficulty breathing with age-specific tachypnea using WHO classification
Study physicians collected a nasopharyngeal wash sample by attaching a butterfly catheter (needle removed), to a 10 ml syringe containing 5 ml normal saline, placing the child in a 30° semi-Fowler position with the head slightly angled forward, inserting the catheter between 2 and 3 cm into the nares, injecting the saline, and immediately applying suction while removing the catheter
We observed each child from the start of enrollment of the child in the study and continued until the end of the follow-up period (March 2011), until the child left the study, or the family of the child moved out of the study area to reside in some other area. We calculated incidence as the number of new events divided by child-years at risk. For calculating virus-specific incidences of ARI and pneumonia we restricted our analyses to children who were aged <2 years during the follow-up period and divided the child-years in to three age groups (0–6months, 6–12 months and 12–24 months). We used Poisson estimation to calculate incidence and 95% confidence interval around incidences. Using the date of illness onset, and the proportions of viral pathogen detected in the respiratory samples, we plotted timing of viral pneumonia in a histogram.
Our study began in April 2009 and ended in March 2011. We followed 515 children for 730 child-years of observation (median time each child was observed was 1.7 years); 283 (55%) of the children were male. Fifty two (10%) of the 515 children did not complete the study because they migrated out of the study area. Among 515 children, 263(51%) were born after the study began in April 2009. The median age of the cohort at enrollment in to our study was 0.5 months (inter-quartile range [IQR] 0.1–8 months). The median birth weight of the cohort children was 2663 gms (a birth weight of 2500 gm is considered to be standard birth weight)
Sex of the child (male), n (%) | 283 (55%) |
Median birth weight of birth cohort child, grams (IQR) | 2663 gm (IQR 2343–2968 gm) |
Children with weight for age Z-score (WAZ) <−2, n (%) | 137 (27%) |
Children with height for age Z-score (HAZ) <−2, n (%) | 86 (17%) |
Median duration of exclusive breast feeding in months, (IQR) | 4 months (2–6 months) |
Children with mothers without formal education, n (%) | 194 (39%) |
Children with fathers without formal education, n (%) | 185 (37%) |
Among the 515 children followed, 423 (82%) developed 1,322 episodes of respiratory infections during April 2009–March 2011. A total of 918 (69%) of the episodes were classified as ARI and 378 (29%) were diagnosed as pneumonia by the study physician. The remaining 26 (2%) episodes were diagnosed as otitis media or only cough by the study physician. Out of the 223 children who developed at least one episode of pneumonia, 47 (21%) developed two episodes and 22 (10%) developed three episodes. The main presenting symptoms among children diagnosed with pneumonia were cough (100%), tachypnea (100%), reported fever (98%) (53% of the pneumonia episodes also had documented fever), runny nose (97%), difficulty breathing (84%), crepitations (44%) and ronchi (33%). The study physician referred one child (0.3%) with pneumonia to a tertiary children hospital who was hospitalized due to aggravating symptoms even after treatment as per WHO guidelines. There was no other hospitalization associated with ARI or pneumonia and we did not observe any ARI or pneumonia related deaths during the study period.
We identified viral respiratory pathogens in 66% (610 of 918) of ARI episodes and in 77% (293 of 378) of pneumonia episodes (
Viral pathogen | ARI(N = 918)n (%) | Pneumonia(N = 378)n (%) |
Respiratory syncytial virus | 91(10) | 85 (22) |
Rhinoviruses | 119(13) | 46 (12) |
Human metapneumovirus | 48(5) | 41 (11) |
Influenza A/H3 | 40 (4) | 17 (4.5) |
2009 pandemic influenza A (H1N1) virus | 35(4) | 6 (2) |
Influenza B | 45(5) | 3(1) |
Human parainfluenza virus 1 | 25(3) | 6 (2) |
Human parainfluenza virus 3 | 46(5) | 23 (6) |
Adenoviruses | 68(7) | 14 (4) |
Human parainfluenza virus 2 | 11(1) | 4 (1) |
Multiple viruses | 81(9) | 49 (13) |
No virus identified | 308 (34) | 85 (22.5) |
We also identified 41 cases of 2009 pandemic influenza A (2009 H1N1) virus infection among the cohort children. The first child with 2009 H1N1 infection was identified on 12 July, 2009, less than four weeks after the detection of the first 2009 H1N1 case on 19 June 2009 in Bangladesh
The incidence of ARI was 125/100 child-years (95% CI 120–134) and pneumonia was 52/100 child-years (95% CI 47–57) in this cohort of children. The incidence of ARI and pneumonia associated with laboratory-confirmed respiratory virus infection was 80/100 child-years (95% CI 77–90) and 40/100 child-years (95% CI 36–45). Children aged 0–6 months were followed for 140 child-years at risk, children aged 6–12 months for 167 child-years and children aged 12–24 months for 297 child-years. The age-specific annual incidences of pneumonia/100 child-years associated with laboratory-confirmed respiratory virus infection were 32 (95% CI 21–39) for children aged 0–6 months, 51 (95% CI 41–63) for children aged 6–12 months and 44 (95% CI 37–52) for children aged 12–24 months. The annual incidence of pneumonia/100 child-years associated with specific respiratory viruses was 12.5 for RSV, 6 for rhinoviruses, 6 for HMPV, 4 for influenza viruses, 3 for HPIV 3 and 2 for adenoviruses (
ARI/100 child-years (95% CI) | Pneumonia/100 child-years (95% CI) | |||||||
Virus etiology | 0–6months | 6–12months | 12–24months | All age groups | 0–6months | 6–12months | 12–24months | All age groups |
RSV | 8(4–14) | 18(13–26) | 13(10–18) | 13(11–17) | 15(10–23) | 11(7–17) | 12(9–17) | 12.5(10–16) |
Rhinoviruses | 12(7–19) | 27(20–36) | 12(9–17) | 17(14–20) | 3(1–8) | 8(4–13) | 7(5–11) | 6(5–9) |
HMPV | 4(1–9) | 7(4–13) | 9(6–13) | 7(5–10) | 1(0.5–6) | 8(5–14) | 6(4–10) | 6(4–8) |
Influenza | 6(3–12) | 20(14–28) | 16(12–21) | 15(12–18) | 3(1–8) | 5(3–10) | 4(2–7) | 4(3–6) |
HPIV | 1(0.4–6) | 1(0.08–4) | 7(4–10) | 6(4–8) | 1(0.1–5) | 1(0.3–5) | 1(0.3–3) | 3(2–5) |
Adenoviruses | 1(0.1–5) | 13(8–19) | 12.5(9–17) | 10(8–13) | 0 (0.0–4) | 2(1–6) | 3(2–6) | 2(1–3.5) |
Our study suggests that childhood pneumonia is prevalent and viruses, especially RSV, are detected in the majority of urban poor children aged <2 years with pneumonia in Bangladesh. A total of 77% of all the episodes of pneumonia in this cohort had a respiratory virus detected which is similar to findings from other studies of young children where etiological agents of lower respiratory tract infections have been thoroughly investigated
Similar to findings from other studies, RSV was the most frequently identified virus in this cohort of children with pneumonia
Influenza viruses and HMPV were also individually detected in 7% and 9% of episodes of pneumonia. Influenza virus infections were associated with 10% of childhood pneumonia among children aged <5 years in a study conducted in another urban setting of Bangladesh
In our study we observed increase in influenza activity in April–June of 2009 and 2010 which coincides with the influenza seasonality previously described in Bangladesh
Our study has several potential limitations. Our study population was drawn from a single urban community therefore the data may not be generalizable to the whole country. Nevertheless our incidence of pneumonia in this cohort of children was comparable to other studies done in other low-income settings including urban Bangladesh
The study findings demonstrated a high incidence of pneumonia associated with respiratory virus infection among children aged <2 years. These children were under close follow up and received timely treatment and referral services when necessary. Children under such close surveillance are likely to under represent severe illness
International Centre for Diarrhoeal Disease Research, Bangladesh acknowledges with gratitude the commitment of CDC and UVA to its research efforts. The authors would like to thank all the study participants for their contribution in the study. We gratefully acknowledge the relentless effort of the field staffs involved in data collection and compilation. We also acknowledge the contribution of Dorothy Southern and Katherine Sturm-Ramirez's review of this manuscript and Jaynal Abedin's support with the statistical analyses. We are also thankful to W. Abdullah Brooks for his support in developing the study design.