Morbidity and mortality associated to influenza A (H1N1) 2009 admissions in two hospitals of the Metropolitan area and analysis of its economic impact

Influenza A (H1N1) 2009 infection was an important cause of morbidity and mortality in Chile. To characterize the clinical pattern of hospitalized patients, identify risk factors associated with ICU admission or death, and evaluate its economic impact. Twenty five adult patients admitted to 2 hospitals in the Metropolitan Area from May 2009 to December 2010 with PCR confirmed H1N1 infection were analyzed. Total hospital charges were obtained and, using data of registered cases, expenses for the whole country during the first epidemic wave were estimated. Aill cases presented a risk factor: age over 60 years old (n = 13, 52%), co-morbid conditions (n = 24, 96%) or pregnancy (n = 1, 4%). Pneumonia was present in 64% (n = 16) and 16% (n = 4) had hypotension. Only 6 patients (24%) had a CURB-65 score ≥ 2 and 36% (n = 9) requiring ICU admission. Case fatality rate was 16% (n = 4). By multivariate analysis, diabetes mellitus type 2 was independently associated with ICU admission or death (OR 8.12; IC95 1.11-59.2, p < 0.05). Hospital charges for those admitted to ICU or the intermediate care unit reached US$ 20,304, and US$ 1,262 for those admitted in general wards. We estimated US$ 20 million in hospital charges for influenza related hospitalizations during the first wave for the whole country. A high proportion of patients affected by influenza A (H1N1) 2009 infection required ICU admission during 2009-2010. Case fatality rate associated to this infection was high, and diabetes mellitus type 2 was a risk factor for ICU admission or death. Hospital charges were higher for those admitted in critical care units and represented an important expenditure for Chile during the first wave. The CURB-65 score was inappropriate to recognize patients at risk of hospitalization or ICU admission.