Prospective cohort study of patients with a confirmed CHIKV infection (positive RT-PCR for CHIKV on the sample at the time of inclusion or seroconversion defined as positive anti-CHIKV Immunoglobulin M (IgM) antibody assay on day 14), who attend the outpatient clinic of the Institute of Tropical Medicine in Antwerp and the Horacio Oduber Hospitaal in Aruba within 72 hours after fever onset. After signing informed consent, clinical and epidemiological data will be recorded in a standardized Case Record Form. Baseline blood and urine samples will be collected as required for routine clinical evaluation of the individual case; sampling will include serum CHIKV serologic assays, CHIKV E1 (or similar rapid test), as well as serum and urine for RT-PCR for CHIKV. After the initial evaluation, suspected CHIKV cases are scheduled for biweekly serum and urine collection for RT-PCR for CHIKV for a duration of 2 weeks, then after 3, 4 and 12 weeks. Serum at 4 weeks will be used for second serologic assay. Suspected cases that test negative for CHIKV by RT-PCR on serum will be excluded.