Korean J Clin Microbiol.  2010 Sep;13(3):103-108. 10.5145/KJCM.2010.13.3.103.

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

• Yoo SJ
• Noh CH
• Yoo HM
• Shin WC
• Choi SJ
• Kim BN
• Kim CK
• Chey MJ
• Kim K
• Lee SL
• Kuak EY
• Shin BM

• KMID: 1461617
• DOI: http://doi.org/10.5145/KJCM.2010.13.3.103

Abstract

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.

Keyword

Influenza A virus; Swine-origin influenza; H1N1

MeSH Terms

Adolescent
Child
Cough
Delivery of Health Care
Family Characteristics
Fever
Hospitalization
Humans
Influenza A virus
Influenza, Human
Korea
Nose
Oseltamivir
Pharyngitis
Seasons
Viruses
Oseltamivir

Figure

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  Fig. 1. Daily numbers of patients who visited the influenza clinic due to acute febrile respiratory illnessess (N=5,322), patients with PCR-confirmed S-OIV (N=309), and patients with PCR or rapid influenza A antigen positive results (N=491), August to September 2009. Abrupt increase of the visits to the influenza clinic was observed at the end of August, and it followed by the increase of S-OIV patients.

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