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

Abstract

BackgroundRecent 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 FindingsWe 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/SignificanceOur 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.

Characterization of influenza virus among influenza like illness cases in Mumbai, India

“…1a). Similar findings were obtained during the year 2007-2008 in a study was carried out on National hospital based surveillance in Bangladesh and National Institute of Cholera and Enteric Disease (NICED) in Kolkata [1,12].…”

Concurrent Pneumonia in Children Under 5 Years of Age Presenting to a Diarrheal Hospital in Dhaka, Bangladesh

“…In Bangladesh, influenza and influenza-like illnesses occur mostly during the rainy season of June-September. 21 Thus, the high rates of concurrent pneumonia in November, and the low rates seen in December, are unexpected and likely unrelated to seasonality of respiratory viruses. Nevertheless, given the seasonality of various diarrheal and respiratory pathogens in Bangladesh, we selected controls matched for month of admission.…”

Influenza seasonality and vaccination timing in tropical and subtropical areas of southern and south-eastern Asia

“…These findings are consistent with the reports from the countries. 13,[16][17][18][19][20][21][22][23][24][25][26][27] Host-related and environmental factors (e.g. lower temperatures and decreased humidity) may influence both viral transmission and host susceptibility.…”

“…14 FluNet data are regularly collected by surveillance systems in geographically disparate sentinel sites that register cases of influenza-like illness or severe acute respiratory infection. 13,[16][17][18][19][20][21][22][23][24][25][26][27] Data on specimen positivity and on viral subtypes were based upon specimens from these surveillance systems; all samples were tested using reverse transcription polymerase chain reaction assays, 28 with the exception of samples from India collected before 2009, which were tested with viral isolation methods. …”