Because of this difference, we performed subgroup analysis on the 100 chikungunya patients diagnosed by RT-PCR or IgM seroconversion who completed follow-up (45 with arthralgia lasting >3 months and 55 with arthralgia lasting ≤3 months) and found that CXCL8 (RR=1.01; 95% CI: 1.00-1.01) and IL-6 (RR=1.03; 95% CI: 1.00-1.06) levels were associated with chronic arthralgia in bivariate Poisson models. The gene discussed is CXCL8; the disease is Arthralgia.