in Africa. ATL is relatively uncommon among those infected with HTLV-1. The overall incidence of ATL is estimated at 1 per 1,500 adult HTLV-1 carriers per year. Those cases that have been reported have occurred mostly among persons from the Caribbean or blacks from the Southeast (National Institutes of Health, unpublished data). There appears to be a long latent period between HTLV-1 infection and the start of ATL. Research Novel approaches to the treatment of PTCL in the relapsed or refractory setting are under investigation. Pralatrexate is one compound currently under investigations for the treatment of PTCL. References Further reading Genoveffa Franchini's NCI page: Human Retroviral Diseases: Pathogenesis and Prevention International Retrovirology Association External links Acute lymphocytic leukemia Animal viral diseases Rare cancers Sexually transmitted diseases and infections Lymphoma