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

Novel influenza A (H1N1) virus emerged in April, 2009, spread rapidly to become pandemic by June, 2009. To study the clinco-epidemiological profile of pH1N1and seasonal influenza (SI) from 2009 to 2013. Retrospective, hospital-based study was done by reviewing medical records for collecting demographic and clinical profile of the study samples. 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. We observed seasonal variation, cocirculation, similar clinical features, decreased virulence, and community spread with respect to pH1N1 and SI from 2009-2013.