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.


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.
Zaman
Rashid Uz
RU
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh. zaman.rashid@gmail.com
Alamgir
A S M
AS
Rahman
Mustafizur
M
Azziz-Baumgartner
Eduardo
E
Gurley
Emily S
ES
Sharker
M Abu Yushuf
MA
Brooks
W Abdullah
WA
Azim
Tasnim
T
Fry
Alicia M
AM
Lindstrom
Stephen
S
Gubareva
Larisa V
LV
Xu
Xiyan
X
Garten
Rebecca J
RJ
Hossain
M Jahangir
MJ
Khan
Salah Uddin
SU
Faruque
Labib Imran
LI
Ameer
Syeda Shegufta
SS
Klimov
Alexander I
AI
Rahman
Mahmudur
M
Luby
Stephen P
SP
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