Epidemiology and Infection

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Epidemiology and Infection (2010), 138:199-209 Cambridge University Press
Copyright © Cambridge University Press 2009 This is a work of the U.S. Government and is not subject to copyright protection in the United States
doi:10.1017/S095026880999063X

Original Papers

Influenza

Influenza epidemiology and characterization of influenza viruses in patients seeking treatment for acute fever in Cambodia


P. J. BLAIRa1, T. F. WIERZBAa2, S. TOUCHa3, S. VONTHANAKa4, X. XUa5, R. J. GARTENa5, M. A. OKOMO-ADHIAMBOa5, A. I. KLIMOVa5, M. R. KASPERa1 and S. D. PUTNAMa1 c1

a1 U.S. Naval Medical Research Unit No. 2, Jakarta, Indonesia
a2 U.S. Naval Medical Research Unit No. 2, Phnom Penh, Kingdom of Cambodia
a3 Communicable Diseases Control Department, Kingdom of Cambodia Ministry of Health, Phnom Penh, Kingdom of Cambodia
a4 National Institute of Public Health, Kingdom of Cambodia Ministry of Health, Phnom Penh, Kingdom of Cambodia
a5 Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA
Article author query
blair pj [PubMed]  [Google Scholar]
wierzba tf [PubMed]  [Google Scholar]
touch s [PubMed]  [Google Scholar]
vonthanak s [PubMed]  [Google Scholar]
xu x [PubMed]  [Google Scholar]
garten rj [PubMed]  [Google Scholar]
okomo-adhiambo ma [PubMed]  [Google Scholar]
klimov ai [PubMed]  [Google Scholar]
kasper mr [PubMed]  [Google Scholar]
putnam sd [PubMed]  [Google Scholar]

SUMMARY

The epidemiology, symptomology, and viral aetiology of endemic influenza remain largely uncharacterized in Cambodia. In December 2006, we established passive hospital-based surveillance to identify the causes of acute undifferentiated fever in patients seeking healthcare. Fever was defined as tympanic membrane temperature >38°C. From December 2006 to December 2008, 4233 patients were screened for influenza virus by real-time reverse-transcriptase polymerase chain reaction (rRT–PCR). Of these patients, 1151 (27·2%) were positive for influenza. Cough (68·8% vs. 50·5%, P<0·0001) and sore throat (55·0% vs. 41·9%, P<0·0001) were more often associated with laboratory-confirmed influenza-infected patients compared to influenza-negative enrollees. A clear influenza season was evident between July and December with a peak during the rainy season. Influenza A and B viruses were identified in 768 (66·3%) and 388 (33·7%) of the influenza-positive population (n=1153), respectively. In December 2008, passive surveillance identified infection of the avian influenza virus H5N1 in a 19-year-old farmer from Kandal province who subsequently recovered. From a subset of diagnostic samples submitted in 2007, 15 A(H1N1), seven A(H3N2) and seven B viruses were isolated. The predominant subtype tested was influenza A(H1N1), with the majority antigenically related to the A/Solomon Island/03/2006 vaccine strain. The influenza A(H3N2) isolates and influenza B viruses analysed were closely related to A/Brisbane/10/2007 or B/Ohio/01/2005 (B/Victoria/2/87-lineage) vaccine strains, respectively. Phylogenetic analysis of the HA1 region of the HA gene of influenza A(H1N1) viruses demonstrated that the Cambodian isolates belonged to clade 2C along with representative H1N1 viruses circulating in SE Asia at the time. These viruses remained sensitive to oseltamivir. In total, our data suggest that viral influenza infections contribute to nearly one-fifth of acute febrile illnesses and demonstrate the importance of influenza surveillance in Cambodia.

(Accepted July 24 2009)

(Online publication August 24 2009)

Key Words:Avian flu; Cambodia; epidemiology; influenza

Correspondence:

c1 Author for correspondence: Dr S. D. Putnam, JMI Laboratories, 345 Beaver Kreek Centre, North Liberty, IA 52240, USA. (Email: shan8299@hotmail.com)


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