[Speculation on reasons why co-infection of tuberculosis and HIV is rather rare in Japan].

Co-infection of tuberculosis (TB) and HIV is a serious problem in most developing countries and in industrialized countries, co-infection of TB and HIV is seen mainly among migrant population. In case of Japan, the numbers of both new HIV infection and AIDS cases have been increasing except slight decline in both figures in 2012, however, the epidemiological situation of HIV and AIDS is still one of the lowest in the world, and among index diseases of AIDS, TB is 5th among Japanese. Based on prevalence of radiological TB findings in the national TB prevalence survey in 1968 and the coverage of BCG vaccination, the author speculated that most TB primary infection took place among those with rather high delayed type sensitivity, thus formation of typical primary complex was rather rare and the number of tubercle bacilli in primary complex and post-primary early disseminated lesions were few, and less risk of development of active TB even among HIV infected individuals.