TABLE 3.
Transmission route | Risk factor (references) |
---|---|
Maternal exposure | Breastfeeding duration, particularly longer than 6 mo (116, 239–244) |
Higher maternal HTLV-1 proviral load (234, 245–247, 249, 250) | |
Sexual intercourse | Condomless sex (254) |
Earlier age at first sex (262) | |
No. of partners (261) | |
Current or past sexually transmissible infections (102, 254, 258, 259, 261, 468)a | |
Sex during menses and vaginal douching pre- and postintercourse (102) | |
Higher HTLV-1 proviral load (253, 254, 256, 257) | |
Duration of sexual relationship (253, 254) | |
Therapeutic use of blood products | Shorter storage duration (266, 268, 269) |
It is difficult to distinguish sexually transmitted infections as a cofactor for HTLV-1 transmission from the alternative explanation that both HTLV-1 and other sexually transmitted infections are driven by sexual behavior as the common causal factor.