Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


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pISSN 2288-0585 eISSN 2288-6850

Outbreak of Swine-Origin Influenza A (H1N1); Experience of a Regional Center in Seoul during a Month, August-September 2009

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2010 September, Volume 13, Issue 3, pages 103-108.

Outbreak of Swine-Origin Influenza A (H1N1); Experience of a Regional Center in Seoul during a Month, August-September 2009

Soo Jin Yoo1, Choong-Hee Noh2,3, Hyeon Mi Yoo2, Won Chang Shin4, Soo Jeon Choi4, Baek-Nam Kim4, Chang Keun Kim5, Myoung-Jae Chey5, Kyunam Kim6, Sang-Lae Lee7, Eun-Young Kuak1, Bo-Moon Shin1,2
Departments of 1Laboratory Medicine, 2Infection Control Office, 3Urology, 4Internal Medicine, 5Pediatrics, 6Family Medicine, and 7Emergency Medicine, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea


Background: The aim of this study is to clarify the epidemiology of swine-origin influenza A (H1N1) virus 2009 (S-OIV) during the first month of outbreak at one of influenza clinic in Seoul, Korea. 

Methods: We documented the epidemiologic and clinical features of S-OIV-confirmed cases who visited a university hospital in Northeastern Seoul between August 21 and September 20, 2009. Nasopharyngeal swab of patients with acute febrile respiratory illnesses were evaluated with rapid influenza antigen tests and multiplex RT-PCR for S-OIV and seasonal influenza A. 

Results: A total of 5,322 patients with acute febrile respiratory illnesses were identified at our influenza clinic for the study period. S-OIV was confirmed in 309 patients by RT-PCR. The patients ranged from 2 months to 61 years of age and 189 patients (61.2%) were teenagers. Eighty-one patients had known contact with S-OIV-confirmed patients in schools (N=61), households (N=15), and healthcare facilities (N=3). Frequent symptoms were fever (94.5%), cough (73.1%), sore throat (52.1%), and rhinorrhea (50.5%). Gastrointestinal symptoms were also present in 10 patients (4.9%). Ten patients (4.9%) required hospitalizations. Seventy patients (22.7%) could not take oseltamivir at the first visits, however, all of them recovered without complication. Rapid antigen tests showed the sensitivity of 44.4% (130/294). Patients with positive antigen tests, compared with negative antigen tests, showed higher frequencies of rhinorrhea (60.8% vs 43.3%, P=0.004) and stuffy nose (33.8% vs 20.1%, P=0.012). 

Conclusion: S-OIV infections spread predominately in school-aged children during the early accelerating phase of the outbreak. Rapid influenza antigen tests were correlated with nasal discharge and obstruction. (Korean J Clin Microbiol 2010;13:103-108)


 Influenza A virus, Swine-origin influenza, H1N1