INTRAFAMILIAL CLUSTERING AND 4-YEAR FOLLOW-UP OF ASYMPTOMATIC HUMAN T-CELL LEUKEMIA-VIRUS TYPE-I (HTLV-I) INFECTION IN BENIN (WEST-AFRICA)

Background Few data exist concerning familial human T-cell leukaemia v irus type I (HTLV-I) carrier states and transmission in African countr ies. Two previous surveys per formed in Benin in 1989 and 1990 using a three-level cluster sampling method allowed us to identify HTLV-I pos itive subjects. The evolution of HTLV-I within the families of these s ubjects is described over a 4-year period, 1991-1995. Methods Since 19 91, 37 HTLV-I seropositive subjects, six subjects with indeterminate W estern-Blot pattern, and their relatives have been followed up once a year clinically and biologically. Results Twenty-three mothers in the study group gave birth to 27 children between 1991 and 1995. Among the 13 infants born to the 12 seropositive mothers, two seroconverted bef ore their second birthday. One adult woman whose husband was seroposit ive developed seropositivity 4 years after marriage. In March 1992, a family case-control study (proband study) was conducted. A seroprevale nce of 27.5% was found among 138 relatives of 32 infected subjects and 1.4% among 142 relatives of 32 control subjects. Conclusions There is clearly an intrafamilial clustering of HTLV-I in Benin. The annual in cidence density of HTLV-I in this cohort is estimated at 6 parts per t housand.