IL18 and infection: Haplotype analysis showed the IL18 −137G/−607A haplotype was more frequent in the infected group compared to the uninfected control group, and the IL18 −137C/−607C haplotype was increased in the control group compared to the others, suggesting that the presence of IL18 −607AC genotype and IL18 −137G/−607A haplotype could be a possible biomarker for increasing the risk factor for infection, in opposition to the presence of IL18 −607CC genotype and −137C/−607C haplotype, that appear to confer protection against HTLV-1.