Influenza has never been perceived as an illness. Now,in their first attempt to assess the influenza disease burden,researchers of National Institute of Virology (NIV) along with Vadu rural health programme of the KEM hospital research centre and Centre for Disease Control and Prevention,Atlanta,USA have conducted a study on 1.20 lakh people across 22 villages in Vadu,which is an hours drive from Pune. There has been a significant disease burden of influenza among hospitalized patients,the preliminary findings of their ongoing study said. Presenting their findings at a recently concluded conference on emerging infectious diseases at Atlanta,USA,Dr AC Mishra,Director of NIV and Dr MS Chadda,Deputy Director of NIV said that due to the wide clinical spectrum of influenza,giving a syndromic case definition for influenza surveillance was still a matter of considerable debate. The influenza can be present in various forms depending on the patients age and virus sub-type. Between May 2009 to April 2011,we had enrolled hospital admissions with patients having acute medical illness,including acute exacerbations of pre-existing chronic illness. Nasal and throat swab specimens were tested for influenza. Among the 3,291 enrolled patients suspected for influenza,667 (20%) tested positive. Fever was the most common symptom in both influenza positive (96%) and negative (93%) patients. Cough (93% and 79%) and sore throat (58% and 37%) were more common in influenza positive than influenza negative patients. Difficulty in breathing was seen in less than 5% of influenza positive patients. Our initial findings suggest that replacing measured fever by reported fever increases the sensitivity,but decreases the specificity of influenza like illness definition for finding laboratory-confirmed influenza. The severe acute respiratory infection and acute respiratory infection case definition,(which includes difficulty in breathing) results in missing influenza cases and underestimating the true disease burden,researchers pointed out. According to Dr AC Mishra,Director of NIV,this is an ongoing study to understand the burden of influenza in the community. Three sites are being monitored at Vadu. Due to the surveillance system we have started picking up H1N1 virus infection cases from March. However,it was not an isolated pocket and the activity was evident across the city and in the outskirts,he pointed out. It could be a short spell,but as part of our study we are also looking at the economic burden to the patients,he added.
