Complications and Outcome of H1N1 Influenza in a Tertiary Care Hospital in South India A Retrospective Study

Background: Influenza virus causes a highly contagious febrile illness ranging from mild symptoms to acute respiratory distress syndrome, respiratory failure and death. The H1N1 influenza pandemic caused a worldwide public health challenge. Objectives: This study aimed to record the clinical outcomes and factors associated with poorer outcomes in hospitalized patients. Materials and Methods: Patients with laboratory-confirmed H1N1 infection by real-time polymerase chain reaction were included in this retrospective study. Data regarding the demographics, medical comorbidities, complications, treatment details and outcome were obtained. Statistical analysis was performed using SPSS version 16. Results: Among 295 patients, 143 (48.5%) were males and 152 (51.5%) were females. The majority were in the age group of 18 to 49 years. Pneumonia (8.1%) and respiratory failure (9.2%) were the most frequent complications. A majority (71%) required hospitalization of fewer than 5 days and 32 (10.8%) required ventilatory support. There were no deaths reported in this group. Elderly patients (age>50 years) (P= 0.002) with the presence of comorbidities (P= 0.000) had greater complications. Elderly patients (P= 0.011) with the presence of co-morbidities (P= 0.000) required a longer duration of Oseltamivir treatment. Female patients (P= 0.015) and patients with comorbidities (P= 0.001) had greater ventilator requirements. Elderly (P= 0.002), female patients (P= 0.018), and those with comorbidities (P= 0.000) required a longer hospital stay. Patients with cardiovascular diseases and pre-existing lung diseases had overall poorer outcomes. Conclusion: The main risk factors were old age, female sex, cardiovascular diseases, Chronic Obstructive Pulmonary Disease, and asthma. These parameters were significantly associated with increased Oseltamivir treatment duration, greater complications, prolonged hospital stay and ventilatory support.