A Study on H1N1 Influenza in Adults: Clinical and Laboratory Profiles, and Treatment Outcomes at a Tertiary Care Hospital in Southern India

Introduction. The H1N1 influenza virus, a subtype of influenza A virus, is transmitted from one person another via respiratory droplets. The H1N1 influenza virus usually causes upper respiratory tract infection, leading to runny nose, chills, fever, and poor appetite. In a few cases, it may progress into lower respiratory tract infection, with severe complications including acute respiratory distress syndrome, which can result in respiratory failure and may require mechanical ventilation. Aim and objectives. The study was conducted with the aim of analysing the clinical features, laboratory profile, and treatment outcome of H1N1 influenza infection in adults at a tertiary care hospital of South India. The study had following objectives: 1.) to describe the clinical profile of H1N1 influenza-affected patients, 2.) to evaluate the laboratory findings and complications among H1N1-infected patients, and 3.) to assess the response to treatment and clinical outcomes in patients with H1N1influenza. Materials and Methods. This single-center, retrospective study was conducted in the Department of Internal Medicine at a tertiary care teaching hospital over a one-year period, from April 9, 2019 to April 8, 2020. It included a retrospective review of the medical records of hospitalized patients with confirmed H1N1 infection from June 2017 to December 2018. After selecting patients who met the inclusion and exclusion criteria, we analysed treatment response and clinical outcomes. Results. With increasing age, the probability of complications and the risk of mortality increased significantly. Pregnant women did not show an increased risk of complications compared to non-pregnant women. Patients with abnormalities on chest radiographs had a higher risk of complications and poorer clinical outcomes. Conclusion. The severity of the disease was greater in the elderly population and correlated with longer delays between symptom onset and hospital admission. The requirement of ventilatory support was associated with increased severity of the disease. In contrast, patients with a normal baseline chest X-ray were less likely to develop complications.