Travellers returning from tropical countries often present to emergency departments with acute fever. While systematic screening for malaria is well established in clinical practice in France, further diagnostic testing for infectious diseases is less codified. In addition, the clinical presentation of many tropical and emerging infectious diseases is often similar, making a positive diagnosis in these patients challenging. Improving the microbiological diagnostic strategy for febrile travellers is crucial because the lack of an accurate diagnosis in many of these patients prevents the implementation of appropriate diagnostic and therapeutic measures. These measures include antimicrobial treatment, but also additional investigations, specialised monitoring and the initiation of follow-up of acute or chronic infections. In addition, the current diagnostic approach to tropical fevers is poorly suited to detect outbreaks associated with a new or re-emerging infectious disease and to alert public health authorities in a timely manner. Therefore, this project aims to evaluate the impact of a systematic and expanded microbiological diagnostic strategy for patients presenting to the emergency department with fever after returning from tropical countries. To evaluate this testing strategy, the investigators propose to conduct a multicentre, cluster-randomised, cross-over trial comparing standard care with a systematic microbiological diagnostic algorithm added to standard care.