Incidence of human T lymphotropic virus type I seroconversion after age 40 among Japanese residents in an area where the virus is endemic.
To clarify how seroconversion after age 40 years contributes to the seroprevalence of human T lymphotropic virus type I (HTLV-I), Japanese residents were studied in an area of Kyushu in which HTLV-I is endemic. Cross-sectional data showed higher seroprevalences among subjects > or = 40 than in those < 40 years old (27.0% vs. 7.9%). The prevalence was also greater in women than men (25.5% vs. 17.6%). Six hundred subjects > or = 40 years old were tested during 1976-1993. Among 8 who seroconverted, 5 had an HTLV-seropositive spouse and 2 seroconverted after blood transfusions. The incidences per 1000 person-years of seroconversion in age groups 40-49, 50-59, and > or = 60 years were, respectively, 0.0, 0.0, and 3.3 (range, 1.38-5.13) in men and 0.0, 5.3 (range, 0.11-7.99), and 1.4 (range, 0.00-1.60) in women. The seroconversion incidence was insufficient to account for the rise of seroprevalence in those > or = 40 years old, especially among women. These results suggest that the high rate and sex discordance in HTLV-I seroprevalence after age 40 may depend mainly on the birth cohort effect for vertical or horizontal transmission.
Takezaki
T
T
Division of Epidemiology, Aichi Cancer Center Research Institute, Nagoya, Japan.
Tajima
K
K
Komoda
H
H
Imai
J
J
D000328:Adult; D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D015481:HTLV-I Antibodies / Q000097:blood*; D015490:HTLV-I Infections / Q000635:transmission; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015819:Substance Abuse, Intravenous / Q000150:complications; D065227:Transfusion Reaction
D015481:HTLV-I Antibodies