[Seroprevalence of HTLV-I in relatives of patients with spastic paraparesis (HAM/TSP and PEP)].

The seroprevalence of HTLV-1 was studied in parents, brothers, siblings and sexual partners of 147 patients with spastic paraparesis associated to HTLV-1 (HAM/TSP) and 84 patients with HTLV-1 negative spastic paraparesis (SP). Seroprevalence was 29.1% for HAM/SP and 0% for SP relatives (p < 0.001); the last figure is similar to that of the general population. Seroprevalence in sexual partners was 65%, suggesting that sexual intercourse is the principal route of transmission. Likewise, seroprevalence in siblings of mothers with HAM/TSP or HTLV-1 positive was 17.6%, suggesting a high maternal transmission.