Based on the sentinel surveillance networks for influenza-like illness (ILI) and severe acute respiratory infections (SARI), the 2022-2023 season was characterized by the circulation of several respiratory viruses with epidemic waves overlapping each others. Respiratory syncytial virus was responsible for an epidemic wave in November-December 2022, coinciding with a small wave of human metapneumovirus, but it continued to circulate in January 2023. Influenza viruses were responsible for a first epidemic wave at the end of December 2022 - so slightly earlier than during the seasons preceding the COVID-19 pandemic - which was followed by a second small wave in January-February 2023. Seasonal influenza A viruses of the H1N1pdm09 and H3N2 subtypes, and influenza B virus of the Victoria lineage co-circulated without clear dominance. SARS-CoV-2 virus continued to circulate during the whole period but a higher intensity of circulation was detected in March 2023, as well as in August 2023. Parainfluenza viruses were responsible for a small epidemic wave in May 2023. Other respiratory viruses such as seasonal coronaviruses, rhino- and enteroviruses, and adenoviruses were also regularly detected.
Epidemic waves of respiratory syncytial virus and influenza viruses occurred at periods that were close to historical data, indicating that the seasonality of these viruses might be returning to normal following the disruptions due to the COVID-19 pandemic. SARS-CoV-2 coronavirus still circulate without a clear seasonal pattern, but seems to cause smaller epidemic waves than during the pandemic phase. Surveillance all year round with multi-virus testing proves useful to better understand seasonality and interference of the different respiratory viruses.
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