Trend in Age Distribution of Visitors to Flu-Clinics during the Pandemic Influenza (H1N1 2009)

The pandemic influenza (H1N1 2009) virus, after being introduced in Korea in April, 2009, spread rapidly nationwide in mid2009. This study was conducted to characterize trend in age distribution of visitors to Flu clinics during the pandemic. Demographic, clinical and laboratory data of visitors to flu clinic from Week 36 to 52 (August 30 to December 26) of 2009 were retrieved and collected from electronic databases at 9 hospitals. Visitors 0 6, 7 12, 13 18, 19 29, 30 64, and 65 years or more of age were classified into group I to VI, respectively. A total of 107,467 visitors were seen at Flu clinics for a 17 week study period. Of those, 32,485 were laboratory confirmed. Antivirals were prescribed for 62,533 visitors. Numbers of visits, prescriptions of antivirals, and laboratory confirmed cases of the pandemic influenza (H1N1 2009) peaked at Week 44. A large number of visits by group II and III were followed by those of group I and V, especially around the peak. Numbers of visits by group VI were lowest in all hospitals. In some hospitals, higher number of visits lasted longer in children than in adults while vice versa in other hospitals depending on the location. In summary, the pandemic influenza (H1N1 2009) was presumed to peak in late October and involved majorly children and students in Korea. Unique age distribution of visitors to flu clinic was observed in some hospitals.