Last reviewed 01/2018

There are two retroviruses in the oncoretroviridae group which cause human disease; these are type I and type II human T-cell lymphotropic virus (HTLV).

HTLV was the first human retrovirus to be isolated. It is spread by sexual contact, from mother to child and through contaminated blood products.

HTLV-I is endemic in southern Japan, equatorial Africa and South America.

HTLV is able to avoid clearance by the host's immune system by remaining in the latent state, as a provirus within the host's genome.