The RAPID-ARIED Trial is a pragmatic, single-centre, parallel group, open-label,randomised controlled trial to be conducted in the Accident and Emergency Department ofQueen Mary Hospital in Hong Kong. The investigators aim to 1) to evaluate the clinicalimpact of the routine application of point-of-care polymerase chain reaction (PCR)testing for targeted respiratory pathogens in the emergency department (ED) for adultpatients with acute respiratory infections (ARIs) on the hospital length of stay (LOS),antiviral and antibiotic use during influenza seasons or future waves of COVID-19; and 2)to conduct a health economic analysis of such a strategy.The investigators hypothesise that in adult patients hospitalised from the ED for ARIsduring influenza seasons or COVID-19 waves, routine point-of-care PCR test for influenzaA&B, SARS-CoV-2 and respiratory syncytial virus in the ED reduces the hospital LOSsignificantly and cost effectively compared to usual care.In total, 1,050 adult patients who are intended to be admitted to hospital with ARIs inthe ED will be recruited during influenza seasons or future waves of COVID-19 over 36months from 2025 to 2027.Participants will be randomised (1:1 ratio) into the interventional group and controlgroup. A nasal swab will be collected. In the intervention group, research staff willperform PCR test using the GeneXpert® Xpress PCR kit in the ED and communicate the testresults to the patient and the clinical team. In the control group, all microbiologytests will be determined by the clinical team, with retrospective PCR testing of thenasal swab sample after 28 days.The primary outcome is the median hospital LOS. Secondary outcomes include antivirals andantibiotics use and administration time, mortality, and quality-adjusted life year,assessed using the EQ-5D-5L questionnaire.Intention-to-treat analysis (superiority framework) and cost-effectiveness analysis (fromhealthcare provider perspective) will be conducted.Study results will provide evidence regarding the optimal PCR testing strategy in thefuture influenza seasons and COVID-19 waves.