Clinico-Epidemiological Profile, Pandemic Influenza A H1N1/2009 and Seasonal Influenza, August 2009-March 2013, Himachal Pradesh, India.

Background: Novel influenza A (H1N1) virus emerged in April, 2009, spread rapidly to become pandemic by June, 2009. Objective: To study the clinco-epidemiological profile of pH1N1and seasonal influenza (SI) from 2009 to 2013. Materials and Methods : Retrospective, hospital-based study was done by reviewing medical records for collecting demographic and clinical profile of the study samples. Result: Out of 969 samples, positivity and case fatality for pH1N1 and SI was 9.39 and 20.87% vs 11.76 and 7.89%, respectively. Among pH1N1and SI, sex distribution, mean age, and age group involved were 54.95% females, 37.10 years, and 20-29 years (23.08%) vs 43.86% females, 40.32 years, and 20-29 years (22.81%), respectively. Mortality shift was observed from younger to older and healthier, 75% to comorbid, 100% from 2009-2010 to 2012-13 for pH1N1. Conclusion: We observed seasonal variation, cocirculation, similar clinical features, decreased virulence, and community spread with respect to pH1N1 and SI from 2009-2013.