Detection of circulating Influenza A and B virus by real-time reverse transcriptase polymerase chain reaction at a tertiary care center in Chennai, Tamil Nadu, India

Abstract

Objective: The aim of this study was to determine the proportion of influenza-like illnesses (ILIs) caused by influenza A and influenza A H1N1 and to determine the proportion of influenza B in a smaller group of samples with ILIs and influenza A H1N1 negative by qualitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) using TaqMan-based assay at a tertiary health-care center in Chennai, Tamil Nadu. Material and Methods: Laboratory samples of participants from all age groups who had ILIs were included in this study. The study was conducted from January 2018 to January 2019 at a tertiary health-care center in Chennai, Tamil Nadu. The sample size of the study was 1755. This is a cross-sectional study. RNA extraction was performed using QIAamp Viral RNA Mini Kit (Qiagen, U.S.A) as per the manufacturer instructions. The assay is a TaqMan®-based real-time detection of circulating novel influenza A H1N1 and H3N2. Real-time PCR for influenza B virus was performed in influenza A H1N1-negative patients using artus Infl/H1 LC/RG RT-PCR kit (Cat 4523003, Qiagen, Germany). Samples that had a crossing threshold value 15–35 cycles were considered positive. Results: The majority of the participants were in the pediatric and young adult age group (<30 years) (41%). The incidence of influenza was in the range of 32.34–41% up to 60 years. Beyond 60 years, the frequency of detection reduced to 25.9%, and in those above 71 years, it was 22.3%. About 45.4% (n = 798) were positive for influenza A, of which 32.7% (n = 575) were positive for influenza A H1N1. Both influenza A H1N1 and influenza A other than H1N1 incidence started to rise in September and spiked between October and December. Among patients with persistent ILI, screening for influenza B was done in 48 samples. Among 48 samples, 18% (n = 8) had influenza B. Conclusion: The need for increased vaccination is demonstrated through the high influenza A H1N1 positivity rate among pediatric patients with ILIs. Detection of influenza B among influenza A H1N1-negative individuals demonstrates the need for influenza B screening. Incidence of influenza is highest in cooler months. The implementation of vaccination against influenza before the beginning of the cooler seasons could possibly reduce the burden of influenza on the health-care system. The importance of surveillance for the continued screening of influenza could be expanded in the private sector as a majority of the disease burden is observed in that sector.