Retrospective laboratory evaluation of the detection rate of CHIKV infection by real-time Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) on urine. Urine and serum samples from patients with confirmed CHIKV infections from an endemic area (Aruba) and from ITM will be analyzed. The results will be evaluated on a case-by-case basis: time since onset, patient characteristics, severity of symptoms, serology results.