Clinical Profile of Patients Admitted with Swine-Origin Influenza A (H1N1) Virus Infection: An Experience from A Tertiary Care Hospital

Background: Pandemic influenza A (H1N1) 2009 has posed a serious public health challenge world-wide. H1N1 critical illness mostly affects young patients and is often fatal. Objective: Primary objective was to study clinical profile of the patients admitted with confirmed H1N1 swine flu infection. Secondary objective was to observe the risk factors associated with complications like need of mechanical ventilation and or death among H1N1 infected patients. Material and Methods: A prospective observational study was conducted in a tertiary care teaching hospital from June 2009, to December, 2011. H1N1 infection was confirmed by reverse transcriptase PCR. Statistical analysis was done by SPSS, version 11. Binary logistic regression was used to find out independent risk factors for morbidity. Results: Total 495 patients were tested for H1N1 infection. Among them, 115 (23%) were positive and 88(76%) required admission. Median age of cohort was 29 years and 87% of the patients were below 54 years of age. Most common presenting symptoms were fever (98%), followed by cough (86%) and sore throat (54%). Out of 88 patients, 14 (16%) required mechanical ventilation and 6(6.8%) died. Lymphopaenia (Lymphocytes <10%) and presence of patchy infiltrates on chest X-ray (CXR) the time of presentation were independent risk factors associated with need of mechanical ventilation or death in H1N1 infected patients by multivariate analysis. Conclusion: Present study showed that H1N1 swine flu mainly affected people who were <54 years of age. Majority of patients improved with antiviral treatment. Lymphopaenia and CXR which showed bilateral pneumonia at time of presentation were found to be independent risk factors associated with requirement of mechanical ventilation and/or death in H1N1 infection. Pregnant females with flu constituted 33% of total mortality. High priority should be given to such patients. Further community based studies are required to analyze the actual impact of H1N1 infection in the community.