Introduction: Several viruses are accused in the severe acute respiratory infections and their diagnosis profits from the assets of the multiplex PCR (polymerase chain reaction).The aim of this study was to describe the general epidemiology of these infections in hospitalized children and adults and to compare the diagnostic performances of the multiplex to an uniplex PCR.Methodology: Our study included 147 patients hospitalized for severe acute respiratory infections in the IBN SINA University Hospital Center in Rabat between October 2015 and August 2016. The samples were analyzed by multiplex PCR using FTD respiratory pathogens 21 plus and by uniplex PCR. Results:We diagnosed a viral infection in 65% patients and the frequency was significantly higher in the pediatric population (73 vs 46%, p= 0,002). Influenza virus, respiratory syncytial virus (RSV), and human metapneumovirus showed a seasonal peak during the winter season, while enterovirus, adenovirus, parainfluenza virus 3 and rhinovirus do not have marked seasonal variation. Multiple viral infections were identified in 22% of positive cases and were detected only in the pediatric samples and exclusively for the age 0 to 2 years old (p=0.001). The comparison of the multiplex versus the uniplex technique found a perfect technical agreement for the detection of AH1N1 (k = 0.83) and satisfactory agreement for the detection of A / B VRS (k = 0.68). Conclusion:we observed significant differences in viral infection rates and virus types among age groups and seasons and supported the contribution of the multiplex PCR in the diagnosis of severe acute respiratory infections.