Study of Influenza Virus Infection at Tertiary Care Center, Ahmedabad

Description

Abstract (English)

Background: Influenza viruses belong to Orthomyxoviridae family of viruses. Orthomyxoviridae family
viruses are negative-sense ssRNA viruses. Four genera are described; Influenza A, B, C & D. Among this,
Influenza type A infects humans and is responsible for all flu pandemics. In 2009, an Influenza pandemic caused
by a novel strain of H1N1 resulted in millions of infections in more than 214 countries. Since their introduction
in 1968, H3N2 Influenza viruses have undergone extensive genetic and antigenic evolution leading to numerous
seasonal epidemics. In the present study, patients categorized as category C under national Influenza guidelines
and admitted to hospital were screened for Influenza viruses. The aim of current study was to determine the
occurrence of Influenza virus infection, to determine circulating subtype of Influenza virus, to determine
whether the age & gender affects susceptibility to Influenza viruses
Method: In present study, rRT-PCR method was used. As per standard guidelines, received samples were
processed in the Molecular laboratory of Microbiology Department. Viral RNA was extracted from the sample
using automated extraction method (GeneMag Quick Viral DNA/RNA Purification Kit). rRT-PCR reaction
mixture was prepared using Tru PCR kit. The instrument used was CFX96/C1000 Touch Thermal Cycler
System (BIO RAD).
Result: Out of 728 samples received in the laboratory for influenza virus testing, 89 samples were positive for
Influenza virus.88 samples were positive for Influenza A virus and 1 for Influenza B virus from total 89 positive
samples. The most dominant subtype of Influenza A virus was H3N2 53 (60.22%) followed by H1N1 20
(22.72%) and other subtype 15 (17%).Gender wise distribution of subtype does not show any significant
difference. Among 728 samples received, 347 and 381 samples from male & female patients respectively.
Detection of influenza virus was found more in age group of 18 – 60 years as compared to other age group.
Month wise distribution of H3N2 subtype shows that there was sudden increasing trend of this strain from
August 2022 to February 2023.
Conclusion: In present study, an influenza A (H3N2) outbreak was confirmed with a co-circulation of A
(H1N1) pdm09. Positivity rate of H3N2 is slightly higher among male patients and among age group of 18-60
years. Influenza cases were maximum during winter.