Chikungunya virus (CHIKV) appeared for the first time in the Western Hemisphere-the French West Indies-in December of 2013. From there, the virus has spread to other Caribbean islands. Following the diagnosis of first autochthonous CHIKV cases in the Caribbean island of Saint Martin, a large outbreak is ongoing in the Americas. As of September 12, 2014, a total of 706,093 suspected and 9803 confirmed CHIKV cases have been reported in the Americas. This case study highlights the possibility of false-negative immunochromatographic CHIKV immunoglobulin M (IgM) tests and the need of confirmatory tests for suspected cases. Moreover, a greater spread of virus together with the presence of a mosquito vector (Aedes albopictus) enhances the risk of autochthonous transmission in Europe.