title: Influenza in outpatient ILI case-patients in national hospital-based surveillance, Bangladesh, 2007-2008.
abstract: 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.
  
  
  RESULTS
  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
  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.
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh. zaman.rashid@gmail.com
authors.forename: Rashid Uz
authors.initials: RU
authors.lastname: Zaman
authors.forename: A S M
authors.initials: AS
authors.lastname: Alamgir
authors.forename: Mustafizur
authors.initials: M
authors.lastname: Rahman
authors.forename: Eduardo
authors.initials: E
authors.lastname: Azziz-Baumgartner
authors.forename: Emily S
authors.initials: ES
authors.lastname: Gurley
authors.forename: M Abu Yushuf
authors.initials: MA
authors.lastname: Sharker
authors.forename: W Abdullah
authors.initials: WA
authors.lastname: Brooks
authors.forename: Tasnim
authors.initials: T
authors.lastname: Azim
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Fry
authors.forename: Stephen
authors.initials: S
authors.lastname: Lindstrom
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Gubareva
authors.forename: Xiyan
authors.initials: X
authors.lastname: Xu
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Garten
authors.forename: M Jahangir
authors.initials: MJ
authors.lastname: Hossain
authors.forename: Salah Uddin
authors.initials: SU
authors.lastname: Khan
authors.forename: Labib Imran
authors.initials: LI
authors.lastname: Faruque
authors.forename: Syeda Shegufta
authors.initials: SS
authors.lastname: Ameer
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Klimov
authors.forename: Mahmudur
authors.initials: M
authors.lastname: Rahman
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Luby
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001459:Bangladesh / Q000453:epidemiology; D002648:Child; D003710:Demography; D005260:Female; D040362:Geographic Information Systems; D005843:Geography; D006282:Health Personnel; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010045:Outpatients / Q000706:statistics & numerical data*; D011200:Poultry / Q000821:virology; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D018571:Sentinel Surveillance; D055815:Young Adult