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Syphilis is believed to have infected people in 1999 with greater than 90% of cases in the developing world. It affects between 700,000 and 1.6 million pregnancies a year resulting in spontaneous abortions, stillbirths, and congenital syphilis. In Sub-Saharan Africa syphilis contributes to approximately 20% of perinatal deaths.〔 In the developed world, syphilis infections were in decline until the 1980s and 1990s due to widespread use of antibiotics. Since the year 2000, rates of syphilis have been increasing in the US, UK, Australia and Europe primarily among men who have sex with men.〔 This is attributed to unsafe sexual practices.〔 Increased rates among heterosexuals have occurred in China and Russia since the 1990s.〔 Syphilis increases the risk of HIV transmission by two to five times and co-infection is common (30–60% in a number of urban centers).〔 Untreated it has a mortality of 8% to 58% with a greater death rate in males.〔 The symptoms of syphilis have become less severe over the 19th and 20th century in part due to widespread availability of effective treatment and partly due to decreasing virulence of the spirochete. With early treatment few complications result. ==China== In China rates of syphilis have increased from the 1990s to the 2010s. This occurred after a successful campaign to reduce rates was carried out in the 1950s.〔 Rates of diagnosis are higher in urban coastal areas.〔 This may be due to sexual practices or better diagnosis in these areas.〔 Rates of syphilis in 2000–2005 among low-risk groups such as women without children and unmarried people were about 0.3–0.6% while rates among high-risk groups such as drug users and MSM were about 7–15%. Rates are greatest among men who have sex with men and sex workers.〔 The increase has been attributed to a number of factors including: migration from rural communities to urban environments, increased numbers of unmarried men, limited screening for disease, partners not always getting notification, and the fact that high-risk groups frequently do not seek health care.〔 Co-infection of HIV and syphilis is probably a major reason behind resurgence in syphilis prevalence among men who have sex with men in China. It is hypothesized that the association observed between syphilis and HIV among MSM is probably due to similar risks associated with both infections. Analysis of data from a survey among MSM in seven Chinese cities reveal that the factors significantly associated with co-infection are older age, education up to senior high school, unprotected anal intercourse, recent STD symptoms, and incorrect knowledge about routes of transmission. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Epidemiology of syphilis」の詳細全文を読む スポンサード リンク
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