Korean J Infect Dis.
1999 Jun;31(3):210-216.
Epidemiology of Influenza Virus over 8 Years (1990~1998) in Seoul, Korea
- Affiliations
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- 1Department of Pediatrics, Seoul National University College of Medicine, Seoul, Korea.
- 2Department of Pediatrics, Seoul Red Cross Hospital, Seoul, Korea.
- 3Department of Pediatrics, Sungkyunkwan University, Seoul, Korea.
Abstract
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BACKGROUND: Influenza virus is well known to cause recurrent epidemics almost every winter. However, 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), influenza virus types and subtypes, and clinical features in children with influenza virus infection 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 of nasal aspirates. Isolated influenza A viruses were subtyped 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 subtyped influenza A virus, 7 were H1 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 others were bronchiolitis (14.4%), croup (8.2%), and tracheobronchitis (4.1%). Influenza A virus was isolated every winter season. H1 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, i.e., 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 each 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 a long duration. These data may have implications in vaccination policy.
