A. S. M. Alamgir

Influenza in Outpatient ILI Case-Patients in National Hospital-Based Surveillance, Bangladesh, 2007–2008

Background Recent population-based estimates in a Dhaka low-income community suggest that influenza was prevalent among children. To explore the epidemiology and seasonality of influenza throughout the country and among all age groups, we established nationally representative hospital-based surveillance necessary to guide influenza prevention and control efforts. Methodolgy/Principal Findings We conducted influenza-like illness and severe acute respiratory illness sentinel surveillance in 12 hospitals across Bangladesh during May 2007–December 2008. We collected specimens from 3,699 patients, 385 (10%) which were influenza positive by real time RT-PCR. Among the sample-positive patients, 192 (51%) were type A and 188 (49%) were type B. Hemagglutinin subtyping of type A viruses detected 137 (71%) A/H1 and 55 (29%) A/H3, but no A/H5 or other novel influenza strains. The frequency of influenza cases was highest among children aged under 5 years (44%), while the proportions of laboratory confirmed cases was highest among participants aged 11–15 (18%). We applied kriging, a geo-statistical technique, to explore the spatial and temporal spread of influenza and found that, during 2008, influenza was first identified in large port cities and then gradually spread to other parts of the country. We identified a distinct influenza peak during the rainy season (May–September). Conclusions/Significance Our surveillance data confirms that influenza is prevalent throughout Bangladesh, affecting a wide range of ages and causing considerable morbidity and hospital care. A unimodal influenza seasonality may allow Bangladesh to time annual influenza prevention messages and vaccination campaigns to reduce the national influenza burden. To scale-up such national interventions, we need to quantify the national rates of influenza and the economic burden associated with this disease through further studies.

Incidence of influenza-like illness and severe acute respiratory infection during three influenza seasons in Bangladesh, 2008-2010

OBJECTIVE To determine how much influenza contributes to severe acute respiratory illness (SARI), a leading cause of death in children, among people of all ages in Bangladesh. METHODS Physicians obtained nasal and throat swabs to test for influenza virus from patients who were hospitalized within 7 days of the onset of severe acute respiratory infection (SARI) or who consulted as outpatients for influenza-like illness (ILI). A community health care utilization survey was conducted to determine the proportion of hospital catchment area residents who sought care at study hospitals and calculate the incidence of influenza using this denominator. FINDINGS The estimated incidence of SARI associated with influenza in children < 5 years old was 6.7 (95% confidence interval, CI: 0-18.3); 4.4 (95% CI: 0-13.4) and 6.5 per 1000 person-years (95% CI: 0-8.3/1000) during the 2008, 2009 and 2010 influenza seasons, respectively. The incidence of SARI in people aged ≥ 5 years was 1.1 (95% CI: 0.4-2.0) and 1.3 (95% CI: 0.5-2.2) per 10,000 person-years during 2009 and 2010, respectively. The incidence of medically attended, laboratory-confirmed seasonal influenza in outpatients with ILI was 10 (95% CI: 8-14), 6.6 (95% CI: 5-9) and 17 per 100 person-years (95% CI: 13-22) during the 2008, 2009 and 2010 influenza seasons, respectively. CONCLUSION Influenza-like illness is a frequent cause of consultation in the outpatient setting in Bangladesh. Children aged less than  5 years are hospitalized for influenza in greater proportions than children in other age groups.

Incidence of Respiratory Virus-Associated Pneumonia in Urban Poor Young Children of Dhaka, Bangladesh, 2009- 2011

Background 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. Methods 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. Results 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. Conclusion 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.

Avian influenza virus A (H5N1), detected through routine surveillance, in child, Bangladesh.

We identified avian influenza virus A (H5N1) infection in a child in Bangladesh in 2008 by routine influenza surveillance. The virus was of the same clade and phylogenetic subgroup as that circulating among poultry during the period. This case illustrates the value of routine surveillance for detection of novel influenza virus.

Population-Based Incidence of Severe Acute Respiratory Virus Infections among Children Aged <5 Years in Rural Bangladesh, June–October 2010

Background Better understanding the etiology-specific incidence of severe acute respiratory infections (SARIs) in resource-poor, rural settings will help further develop and prioritize prevention strategies. To address this gap in knowledge, we conducted a longitudinal study to estimate the incidence of SARIs among children in rural Bangladesh. Methods During June through October 2010, we followed children aged <5 years in 67 villages to identify those with cough, difficulty breathing, age-specific tachypnea and/or danger signs in the community or admitted to the local hospital. A study physician collected clinical information and obtained nasopharyngeal swabs from all SARI cases and blood for bacterial culture from those hospitalized. We tested swabs for respiratory syncytial virus (RSV), influenza viruses, human metapneumoviruses, adenoviruses and human parainfluenza viruses 1–3 (HPIV) by real-time reverse transcription polymerase chain reaction. We calculated virus-specific SARI incidence by dividing the number of new illnesses by the person-time each child contributed to the study. Results We followed 12,850 children for 279,029 person-weeks (pw) and identified 141 SARI cases; 76 (54%) at their homes and 65 (46%) at the hospital. RSV was associated with 7.9 SARI hospitalizations per 100,000 pw, HPIV3 2.2 hospitalizations/100,000 pw, and influenza 1.1 hospitalizations/100,000 pw. Among non-hospitalized SARI cases, RSV was associated with 10.8 illnesses/100,000 pw, HPIV3 1.8/100,000 pw, influenza 1.4/100,000 pw, and adenoviruses 0.4/100,000 pw. Conclusion Respiratory viruses, particularly RSV, were commonly associated with SARI among children. It may be useful to explore the value of investing in prevention strategies, such as handwashing and respiratory hygiene, to reduce respiratory infections among young children in such settings.

Influenza-associated mortality in 2009 in four sentinel sites in Bangladesh

OBJECTIVE To estimate influenza-associated mortality in Bangladesh in 2009. METHODS In four hospitals in Bangladesh, respiratory samples were collected twice a month throughout 2009 from inpatients aged < 5 years with severe pneumonia and from older inpatients with severe acute respiratory infection. The samples were tested for influenza virus ribonucleic acid (RNA) using polymerase chain reaction. The deaths in 2009 in five randomly selected unions (the smallest administrative units in Bangladesh) in each hospitals catchment area were then investigated using formal records and informal group discussions. The deaths of those who had reportedly died within 14 days of suddenly developing fever with cough and/or a sore throat were assumed to be influenza-associated. The rate of such deaths in 2009 in each of the catchment areas was then estimated from the number of apparently influenza-associated deaths in the sampled unions, the proportion of the sampled inpatients in the local hospital who tested positive for influenza virus RNA, and the estimated number of residents of the sampled unions. FINDINGS Of the 2500 people known to have died in 2009 in all 20 study unions, 346 (14%) reportedly had fever with cough and/or sore throat within 14 days of their deaths. The estimated mean annual influenza-associated mortality in these unions was 11 per 100,000 population: 1.5, 4.0 and 125 deaths per 100,000 among those aged < 5, 5-59 and > 59 years, respectively. CONCLUSION The highest burden of influenza-associated mortality in Bangladesh in 2009 was among the elderly.

Hospital-based prevalence of malaria and dengue in febrile patients in Bangladesh.

We conducted a nationwide study at six tertiary hospitals from December 2008 through November 2009 to investigate etiologies of febrile illnesses in Bangladesh. Febrile patients meeting a clinical case definition were enrolled from inpatient and outpatient medicine and pediatric units. We assessed 720 febrile patients over 12 months; 69 (9.6%) were positive for IgM antibodies against dengue virus by enzyme-linked immunosorbent assay, and four malaria patients (0.56%) were confirmed with immuno-chromatography and microscopic slide tests. We identified dengue cases throughout the year from rural (49%) and urban areas (51%). We followed-up 55 accessible dengue-infected patients two months after their initial enrollment: 45 (82%) patients had fully recovered, 9 (16%) reported ongoing jaundice, fever and/or joint pain, and one died. Dengue infection is widespread across Bangladesh, but malaria is sufficiently uncommon that it should not be assumed as the cause of fever without laboratory confirmation.

Economic burden of influenza-associated hospitalizations and outpatient visits in Bangladesh during 2010.

Understanding the costs of influenza‐associated illness in Bangladesh may help health authorities assess the cost‐effectiveness of influenza prevention programs. We estimated the annual economic burden of influenza‐associated hospitalizations and outpatient visits in Bangladesh.

Seroprevalence of antibodies against highly pathogenic avian influenza A (H5N1) virus among poultry workers in Bangladesh, 2009.

We conducted a cross-sectional study in 2009 to determine the seroprevalence and risk factors for highly pathogenic avian influenza A (H5N1) [HPAI H5N1] virus antibodies among poultry workers at farms and live bird markets with confirmed/suspected poultry outbreaks during 2009 in Bangladesh. We tested sera by microneutralization assay using A/Bangladesh/207095/2008 (H5N1; clade 2.2.2) virus with confirmation by horse red blood cell hemagglutination inhibition and H5-specific Western blot assays. We enrolled 212 workers from 87 farms and 210 workers from three live bird markets. One hundred and two farm workers (48%) culled poultry. One hundred and ninety-three farm workers (91%) and 178 market workers (85%) reported direct contact with poultry that died during a laboratory confirmed HPAI H5N1 poultry farm outbreak or market poultry die-offs from suspected HPAI H5N1. Despite exposure to sick poultry, no farm or market poultry workers were seropositive for HPAI H5N1 virus antibodies (95% confidence interval 0–1%).

Co-circulation of G1, G2 and G9 rotaviruses in hospitalized patients in Bangladesh during 2006-2009.

Rotavirus strain diversity in Bangladesh has been explored since 1985 and as seen in other parts of the world, rotaviruses have shown tremendous strain diversity overtime. Rotavirus antigen was detected in stool specimens using a solid-phase sandwich-type enzyme immunoassay. A multiplex reverse transcription polymerase chain reaction (RT-PCR) was performed for rotavirus G and P genotypes. This current study was carried out between 2006 and 2009 during which time 1,607 (23%) of 7,058 fecal specimens tested positive for group A rotaviruses with the highest incidence rate being observed in winter each year. Genotyping of rotaviruses showed a sharp decline in G2P[4] between 2008 and 2009 with a gradual increase in G1 and G9 strains. Since the Government of Bangladesh is planning to include rotavirus vaccine in the national immunization program, these data on rotavirus strain diversity should be taken into consideration for vaccine strain selection.