Inmaculada Casas
Head of the Respiratory Virus and Influenza Research Group of the Carlos III Health Institute
Respiratory viruses circulating during an epidemic season of respiratory infection allow us to know the dynamics of most acute respiratory infections that in some cases cause hospitalization due to their severity.
Viral detection is performed by genetic analysis systems of one or several viruses simultaneously (RT-PCR), which are increasingly sensitive, influencing the reduction and elimination of unnecessary antibiotic treatments or the implementation of a specific antiviral treatment and its duration.
The analysis of influenza, SARS-CoV-2 and Respiratory Syncytial Virus simultaneously in the laboratories of the different Autonomous Communities generates a specific knowledge of the circulation of each one of them, being the positivity rates to these three viruses one of the markers of the evolution of acute respiratory infections in each of the epidemic seasons.
Apart from the positivity rates, knowledge of the biological and genetic characteristics of the circulating viruses adds to the surveillance system basic information for decision making affecting the control of respiratory infection in the population.
After the 2020 pandemic, SARS-CoV-2 was included in influenza surveillance, extending such surveillance to acute respiratory infection and, as another respiratory virus, its molecular characterization allows us to associate the appearance and circulation of certain lineages, currently the omicron variant, to infection rates in both sentinel and non-sentinel surveillance analyses.
In addition, influenza viruses undergo genetic and antigenic changes, and we can say that sentinel genomic virological surveillance systems have been strengthened in the wake of the covid-19 pandemic.
This season, influenza A/H1N1 viruses are dominant and mostly similar to the A/H1 vaccine component. However, when analyzing the circulating A/H3N2 viruses, which are in the minority, it is observed that they belong to a different genetic group from the group of the vaccine virus in its A/H3 component. Antigenic studies are currently underway.
The integration of the three respiratory viruses through the detection of the new SARS-CoV-2 lineages, the sequencing of influenza in a systematic way with the characterization of its 8 segments of both influenza A and B, and finally the characterization of the possible escape of Respiratory Syncytial Virus to monoclonal antibodies used this season as immunoprophylaxis (Nirsevimab) for the prevention of bronchiolitis, are the main virological novelties presented in the current epidemic season.