RESUMO
BACKGROUND: The world encountered the global outbreak of an H1N1 influenza pandemic in 2009. Influenza has accounted for grave outcomes, not only through infectious complications, but also through the exacerbation of underlying chronic diseases. A substantial number of confirmed or probable cases of influenza had been reported during the 2009 H1N1 pandemic in South Korea, but a review of the development of influenza-related complications or the exacerbation of underlying chronic diseases has been absent. This study aims to understand the influence of the 2009 pandemic on the exacerbation of existing cardiopulmonary diseases. MATERIALS AND METHODS: We surveyed the number of hospitalized patients with a diagnosis of pneumonia, asthma, chronic obstructive pulmonary disease, acute myocardial infarctions, and heart failure during the period of the 2009 H1N1 influenza pandemic in a 950-bed teaching hospital in Korea. Three influenza seasons from 2007 to 2009 were compared via a medical records review. Data collection included the number of hospitalizations, patient age, number of deaths from all causes, and underlying medical conditions of fatal patients. RESULTS: The weekly number of cardiopulmonary hospitalizations showed no differences between the 2009 pandemic influenza period and seasonal influenza epidemics (53 and 56 on average, respectively), but the total number of hospitalized patients during the pandemic influenza period was 1481, whereas there were 625 on average for seasonal influenza. The hospitalization rate for patients under five years of age exceeded that of the patients sixty years of age or older in pandemic influenza, and the hospitalization rate of patients twentyfive to fifty-nine during pandemic influenza was significantly higher than that of seasonal influenza outbreaks (P=0.012). On the other hand, the hospitalization rate of the patients sixty years of age or older during the pandemic influenza period significantly fell short of that in past seasonal influenza periods (P<0.001). However, the patients sixty years of age or older had the highest case fatality rate during both periods. The total number of deaths among hospitalized patients with cardiopulmonary diseases in pandemic influenza and seasonal influenza epidemics was 87 and 46 on average, respectively. Weekly fatal cases were 3 and 4. CONCLUSIONS: The cardiopulmonary hospitalization rate during the pandemic period outnumbered that of preceding seasonal influenza epidemics by its extended length. But, the virulence or disease severity of the 2009 H1N1 and seasonal influenza seems to be little different. A larger-scale epidemiological investigation is necessary.