Interestingly, HTLV-1 infected individuals with the CT/TT allelic variants at the IL28B rs12979860 gene exhibited approximately a 3-fold increased risk of HAM/TSP and had nearly 10-fold higher median HTLV-1 proviral loads (PvLs) than CC carriers [28]. This evidence concerns the gene IFNL3 and tropical spastic paraparesis.