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KMID : 0376120000270010031
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Medical Journal of the Red Cross Hospital
2000 Volume.27 No. 1 p.31 ~ p.39
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Epidemiology of Influenza Virus over 8 Years (1990 ∼1998) in Seoul, Korea
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Abstract
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Background: It is well known that influenza virus has been causing recurrent epidemics almost every winter. However, the information -regarding the epidemiologic pattern of influenza virus in Korea is limited. In this study, the period of influenza virus-isolation each year (1990 --1998), types ´and subtypes and clinical features in children were ´evaluated.
Methods: Epidemiology of influenza virus was studied in. children with lower respiratory tract infections admitted to the Seoul National University Children´s Hospital during the period from 1990 through 1998. Influenza viral infection was diagnosed by viral culture in LLC-MK2 and MDCK cells and/or indirect immunofluorescent staining method with nasal aspirates. Isolated influenza A viruses were subtype by indirect immunofluorescent staining method using monoclonal antibodies which react specifically to H1 or H3 antigen.
Results: Influenza A virus was identified in 76 cases and influenza B virus in 25 cases. Of 62 strains of influenza A virus subtype, 7 strains were Hl subtypes and 54 strains were H3. The occurrence of influenza viral lower respiratory tract infection peaked in infants and children between 6 months and 5 years of age (65%). Pneumonia was the most common manifestation (73.3%) and the others were bronchiolitis (14.4%), croup (8.2%) and tracheobronchitis (4.1 %). Influenza A virus was isolated every winter season. Hl subtype was detected only during 90--91 and 91--92 seasons, while H3 subtype was detected every season. Influenza B virus was isolated every 2 years, such as during 90 -91, 92 --93, 94 -95 and 96 --97 seasons. The period of influenza virus isolation and its peak time varied each season. The first recognized influenza activities were 4 times in November and December, respectively, among the 8 seasons.
Conclusion: The data show that influenza activity in Seoul, Korea begins early in winter months and lasts for long duration. It may have implication for vaccination policy.
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