The prevalence of HTLV-1 infection varies in different parts of the world, whether endemic to those areas or not. There are two main endemic areas worldwide, Southwestern Japan and the Caribbean basin, ranging from 5% to nearly 30% seropositivities. Other parts of the world, such as Central and West Africa, Melanesia, the Middle East, and India, have also been reported to be endemic. Even in the endemic area of Nagasaki district located in Southwestern Japan, the infection rate differs, being only 1-3% in the urban area of Nagasaki and being 15-30% in rural areas in the Goto Islands located in the East China Sea about 100 km from Nagasaki. Most ATL or HAM/TSP have broken out in the endemic areas.
The three principle routes of HTLV-1 transmission include mother-to-child transfer by breast milk, sexual intercourse, and blood product transmission. However, nobody knows why the endemic areas are restricted to certain areas of the world. ATL develops 30-60 years after infection with HTLV-1 during childhood. The lifetime risk in a carrier of HTLV-1 is estimated to be about 5% in ATL and less in HAM/TSP.
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.