The purpose of this study was to identify the etiologic agents associated with Severe Acute Respiratory Infection (SARI) in intubated adult subjects with negative multiplex real-time Polymerase Chain Reaction (PCR) and microbiology results. As isolation of any pathogens is time sensitive, the study evaluated subjects who were culture negative at the time of consent. The study started on April 6, 2017 and it closed on November 1, 2018.