CD40LG and polyarticular arthritis: This apparent persistence of anti-CHIKV IgM is consistent with the observations of both Fourie & Morrison and Gauzere [19,20] who described such persistence of IgM antibodies for up to 12 months in patients suffering from polyarthritis or rheumatoid arthritis after CHIKV infection; and with those of Olivier et al. [21] who recorded 75 and 42% of anti-CHIKV IgM positives, respectively after 7 and 10 months, in French patients with imported CHIKV between 2005 and 2007.