Clinical and Epidemiological Profile of hospitalised H1N1 Cases: Comparison of Pandemic, Post pandemic and Recent epidemic period

Background and objectives: During H1N1 pandemic 2009-2010, numbers of hospital admissions and mortality were high in Gujarat as well as globally. During post pandemic period of 2010-2011, transmission of the influenza A/H1N1 virus was sporadic. In 2013 again there was a sharp rise of influenza 1 cases in Gujarat causing sizable epidemic. Here our aim is to study clinical and epidemiological profile of laboratory confirmed H1N1 positive cases admitted in our hospital during pandemic, post pandemic and recent epidemic period and to study epidemiological trends of this disease. Materials and methods: This retrospective observational study was conducted after due permission from the Intramural Research Committee/Institutional Review Board, Smt NHL Municipal Medical College. We reviewed data of all the patients admitted in our tertiary care hospital with suspected influenza like illness from July 2009 to April 2013. We selected only laboratory confirmed H1N1 positive cases admitted during pandemic (July 2009 to March 2010), Post pandemic (August 2010 to February 2011) and recent epidemic period (December 2012 to April 2013). For each confirmed patient a standardised form was used to collect clinical and demographic data. Results: Out of 339 suspected cases of Category C, 95 patients were laboratory confirmed H1N1 cases. Among them 57(60%) were in pandemic, 14(15%) were in post pandemic and 24(25%) were in Recent epidemic group. Mean age of patients in pandemic (32.5+16.3) was significantly lower than post pandemic and recent epidemic (P value 0.023). Males were older (45+15) and more frequently affected (57%) in post pandemic period than pandemics and recent epidemic. Mean APACHE II score (9.9+4.1), co morbidities (64%) and complications were more in post pandemic than pandemic. In pandemic period mortality was high in young age (25-50yrs), females and pregnant patients while in post pandemic period mortality was high in old age (> 50 yrs), males and patients having co-morbidities (44.4%). Due to delayed presentation, only 9% patients received oseltamivir within 48 hours of symptom onset and another 12% within 72 hours of symptom onset. Conclusion: Our study shows that in post pandemic and recent epidemic period patients were older, with more co morbidities, worse APACHE II score on admission, having more complications and having high mortality than Pandemic period which can be due to drift H1N1 variants and/or emergence of immunity in young population. Delayed presentation to health care facilities is still major obstacle to early treatment of these patients. Continuous surveillance programmes and effective vaccination programmes can help us to prevent excessive morbidity and mortality in community during future epidemics.