<p>The investigation took place in Brazzaville, specifically at the CSI Plateau des 15 ans and Moukondo in the Moungali health district and at the CSI Marien Ngouabi reference sentinel site for influenza in the Talangai health district. This was a descriptive cross-sectional study. The data collection period was from October to December 2021. The population The study was made up of patients who presented symptoms of influenza. The sampling was systematic and the sample size was equal to 90. To collect the data, a form corresponding to the IDSR case definition was used. The techniques used were the use of patient consultation registers to systematically identify cases of influenza to be investigated. Samples were taken from the cases investigated at the CSI Marien Ngouabi and then transferred to the National Public Health Laboratory. Data quality control was done during data entry, data were processed with Excel and then analyzed with Epi info 7.2 software.</p>