title: A prospective comparison of the epidemiological and clinical characteristics of pandemic (H1N1) 2009 influenza A virus and seasonal influenza A viruses in Guangzhou, South China in 2009.
abstract: Comparisons of the clinical characteristics of contemporaneous pandemic (H1N1)  2009 influenza A virus (A(H1N1)pdm09)- and seasonal influenza viruses-infected patients are  important for both clinical management and epidemiological studies. A prospective multicenter  observational study was conducted using a preestablished sentinel surveillance system in  Guangzhou, China during 2009. In this study, the clinical presentations of patients with either  acute respiratory infection or community-acquired pneumonia were recorded, and nasopharyngeal  swab samples were collected for detection of respiratory virus strains using cell cultures or  real-time reverse transcription/real-time polymerase chain reaction. Comparisons of the  clinical features between A(H1N1)pdm09- and seasonal influenza viruses-infected patients were  conducted accordingly. Of the 1,498 patients examined, 265 tested positive for A(H1N1)pdm09,  286 were positive for seasonal influenza A viruses, and 137 for influenza B viruses. The  predominant virus was influenza B before the emergence of A(H1N1)pdm09 (epidemiological week  [EW] 1-EW 21); then, predominantly non-A(H1N1)pdm09 influenza A and, later, A(H1N1)pdm09, which  peaked in EW 46. Compared with the common seasonal influenza-infected patients,  A(H1N1)pdm09-infected patients were younger, and had a higher proportion of these patients  reported prior contact with infected individuals (P < 0.001, by χ(2) test). However, few  significant differences were observed in clinical symptoms and severity among any of the  infections caused by the different influenza A strains. Our hospital-based network served as a  useful source of information during A(H1N1)pdm09 monitoring. Viral distribution in Guangzhou was  characterized by a sharp rise in A(H1N1)pdm09-infected patients in September 2009. Similar to  seasonal influenza A-infected cases, A(H1N1)pdm09 cases had a very small proportion of severe  cases.
authors.affiliation: Macau University of Science and Technology, Faculty of Chinese Medicine, Macau SAR, P.R. China.
authors.forename: Zi-feng
authors.initials: ZF
authors.lastname: Yang
authors.forename: Yang-qing
authors.initials: YQ
authors.lastname: Zhan
authors.forename: Rong-chang
authors.initials: RC
authors.lastname: Chen
authors.forename: Rong
authors.initials: R
authors.lastname: Zhou
authors.forename: Yu-tao
authors.initials: YT
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Luo
authors.forename: Mei
authors.initials: M
authors.lastname: Jiang
authors.forename: Ji-qiang
authors.initials: JQ
authors.lastname: Li
authors.forename: Sheng
authors.initials: S
authors.lastname: Qin
authors.forename: Wen-da
authors.initials: WD
authors.lastname: Guan
authors.forename: Ke-fang
authors.initials: KF
authors.lastname: Lai
authors.forename: Huan-lian
authors.initials: HL
authors.lastname: Wen
authors.forename: Zeng-wei
authors.initials: ZW
authors.lastname: Liang
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Nan-shan
authors.initials: NS
authors.lastname: Zhong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002681:China; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification*; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D012621:Seasons; D018571:Sentinel Surveillance; D055815:Young Adult