Seasonal Variation of Influenza A Virus and Its Subtypes in Patients Attending Tertiary Care Hospital

ABSTRACT

Background:Influenza is an important respiratory infection, causing 250,000 to 500,000 deaths annually. Influenza virus A is the most virulent and associated with winter epidemics in temperate regions, more persistent transmission in the tropics, and occasional large-scale global pandemics. But, there is variability in the pattern, and the H1N1 pandemic of 2009-2010 was unusually with a large spike in spring and a sharp decline continuing throughout winter. Varying in pattern is due to antigenic shift and drift and reassortment of the virus. Methods:A prospective study was carried out in Advance Basic Sciences & Clinical Research Lab, Department of Micro- biology in SMS Medical College & Hospital, Jaipur for diagnosis of Influenza A virus as well as subtyping was done using RT-PCR technique over 1 year period (July 2019 to June 2020) and demographic data was noted. Results:Total of 7213 samples were tested, out of which 498 (6.90%) were positive for Influenza A which is less from the previous year’s 22.46%. Out of total positive cases Influenza a (H1N1) pdm09 was 24.9% and InfA H3N2 was 75.10%. InfA H3N2 was the prominent circulating strain in all months while Influenza a (H1N1) pdm09 was prominent strain pre- vious year. Majority of positive cases were found in March 2020 (43.17%), September 2019 (28.51%). Most of these cases 36.14% were from age group between 20 to 40 years. Conclusions: A decline in the positivity of influenza infection compared to last year is seen which could be in part due to circulation of SARS COV 2 and measures of prevention undertaken by community to prevent it. Demographic parame- ters and seasonal variation of Influenza A virus give ideas to create awareness and to improve control strategies to mini- mize the morbidity, mortality and spread of disease.