A Two Wave Analysis of Hospitalizations and Mortality from Seasonal and Pandemic 2009 A (H1N1) Influenza in Saurashtra, India: 2009-2011

BACKGROUND During May 2009, India reported the confirmed case of 2009 A (H1N1) influenza reported and in August 2009, Saurashtra region made the first report. AIM We describe the clinico-epidemiological characteristics of patients who were hospitalized with 2009 A (H1N1) influenza infection and seasonal influenza in Saurashtra region. SUBJECTS AND METHODS A total of 1726 patients suffering from A (H1N1) influenza and seasonal influenza were admitted in the different hospitals of Rajkot city of Saurashtra region during September 2009-February 2011. Real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR) testing was used to confirm the infection. The clinico-epidemiological features of the patients were closely monitored. Data were analyzed by Chi square or Fisher's exact test, using Epi Info software (version 3.5.1) of the Center for Disease Control (CDC). RESULTS Among the patients hospitalized due to influenza, 29.6% (511/1726) were laboratory confirmed cases of A (H1N1) influenza while the rest 70.4% (1215/1726) were cases of seasonal influenza. A median time of 5 days was observed from the onset of illness to laboratory confirmed diagnosis of A (H1N1) influenza. The median duration of hospital stay of such patients was 2-32 days. All admitted A (H1N1) influenza patients received Oseltamivir drug, but only 14.9% (76/511) received it within 2 days of onset of illness. 24.9% (127/511) of those admitted for A (H1N1) influenza died as compared to 5.3% (65/1215) of those suffering from seasonal influenza. The most common symptoms were cough, fever, sore throat and shortness of breath in both the groups of patients. The prevalence of any coexisting morbidity in those with A (H1N1) influenza was 31.3% (160/511) while in those with seasonal influenza it was 19.4% (236/1215). The common coexisting morbidities were hypertension, diabetes mellitus, chronic pulmonary diseases and pregnancy. Pneumonia was reported in 91% positive patients with chest radiography. CONCLUSION Though the clinico-epidemiological pattern of the A (H1N1) influenza patients were comparable to that of those suffering from seasonal influenza, a fivefold higher mortality was noted in A (H1N1) influenza patients. Hypertension, pregnancy, pneumonia on chest X-ray, and receiving antiviral treatment within 2 days of illness onset were mainly reported among A (H1N1) influenza patients.